Security - Raju Alluri

How fraudsters are using fake Instagram accounts to dupe money

In recent times, there are several instances of fake Instagram accounts duping money from people. The fraudsters use a combination of age old social engineering and impersonation techniques to dupe money.

The impersonation part contains creating a fake social media account (especially Instagram now-a-days, because of the social media’s popularity) and trying to reach out to as many people as possible.

The social engineering part contains showing some sense of urgency after an initial ordinary looking conversation.

Here is a typical sequence of the multiple social media frauds that I witnessed in the recent times.

Fraudster creates a social media account resembling a person with decent number of followers and follows.
- Fraudster picks profile picture from the original account
- Also uses majority of the profile details (profession, links, etc.) for the account, so that it looks legitimate
- The username is a slight variant of the original. Usually a digit or two added at the end of the profile or manage to make it look original by use of special characters
Fraudster follows several people from the original account’s list
Fraudster engages in conversation
- Usually the fraudster starts with general conversation like how things are, where you are, how busy the work is, etc. to earn some trust.
- Fraudster gives you some comfort level in conversation
Fraudster creates sense of urgency regarding a financial matter
- e.g. I need to help someone with real emergency
- e.g. I maxed out on my daily limit, so I need your help
Fraudster gives assurance
- e.g. I will give it to you tomorrow (or next working day) by 7am.
- Usually they pick a time so close to next day, so that there is a general sense of confidence that your money is going to be back within few hours.
Fraudster sends payment/transfer link

The steps might slightly differ, but the modus operandi is almost about the same.

I have seen people falling prey to this type of attack, given the sense of urgency the fraudster can create and how casual the transaction looks like. I almost fell prey to one such thing, but I just called the person who is impersonated and it helped me avoid the money loss.

I also have seen I am being impersonated online. Albeit for a short time, they could create some reasonable inconvenience.

Here are the key things one can do to avoid falling prey to such situations.

Follow only people who you know (even for people who you know online only, make sure that you observe them for some time before you follow them)
Don’t blindly trust any newly created accounts
Don’t always trust the accounts that come up in the top search results. Especially if they are new accounts
Notify the person whose account activity looks suspicious. Especially if there are no (recent) posts, if they are new accounts or if their posts are unusual from what you know
Never send any money without calling the person. Send only upon verification that you are talking to the right person
Never click a link. If you know the other person’s details, directly doing financial transactions with the actual person you know would be better. Even then, make sure that the actual person has full access to the account
If you have a common friend, alert them as well in situations when you are asked for money or asked to click links
Report the account. More people report, more weight it would carry.
Spread the word about the incident. Identify the potential victim groups and tell them what is happening.

By being aware, you may not completely avoid any novice techniques of the fraudsters, but for sure you will be in a position to minimise the impact.

Why this focus on Instagram? Similar things happened on WhatsApp also earlier. However, it is easy to see that the phone number in question is not related to the person you know.

With Instagram, the fraudsters are having a bit more flexibility in terms of reach out and attack vector dimension.

First Rule: Don’t send money. Unless you talk to the individual in person or over a trusted channel – e.g. video call. That helps verify the need and the beneficiary.

Second Rule: Never click a link from these social media conversations. Period.

Brave Browser

01 Jul

Raju Alluri 0 Comment Security, Technical

Started using Brave browser recently. I am quite impressed with the security features. Now a days it is my browser of choice for reading several news and entertainment sites. It limits the eye-catching distractions that are otherwise irksome.

I like the way shields work and I often control the security settings either at global level or for each page. Brave browser is now part of my standard install on desktop clients.

IT, Android One and BYOD

11 Jun

Raju Alluri 0 Comment Brain Dump, Other Opensource, Security, Technical

BYOD (Bring Your Own Device) is now a paradigm that is tightly integrated into IT spectrum. IMO, Android One helps simplify the life of IT staff while handling user owned devices that operate on data that is owned by the organizations.

The IT staff’s ownership over the client devices/end points is reducing very fast in recent years. This is due to the use cases that focus on end users,Â service providers, partners and internal employees that are continuously contributing to the data of an organization. Despite reducing level of ownership of these devices, the IT staff continue to have a responsibility to prove that they have adequate controls over these devices and their data.

For example, signatures of customers and delivery details on delivery personnel’s client devices should be ascertained with to all the integrity and confidentiality controls by IT staff of any shopping website and its delivery partners. There were times when the client devices are custom made solutions for the delivery companies, but smart phones are rapidly replacing these legacy client devices. More often than not, these smart phones are owned and updated by individuals rather than organizations. Hence these BYOD devices pose a challenge to the IT staff and increase threat to the data confidentiality and integrity.

The major challenge for IT staff is to ensure that all the nomadic client devices are running approved, stable and latest stack. In olden days (say about 10 years ago), the client devices are mostly laptops that need to be patched and upgraded regularly, along with appropriate user access controls on these devices. With the proliferation of smart phones as client devices, the challenge goes multi-fold. Wearing an IT Professional’s hat, I do see every smart phone like this:

The moment I think about manageability of that smart phone (not ownership of the smart phone, which is never going to happen), I see the smart phone as

The IT stack in the above picture is a combination of various off-the-shelf and home grown applications, together with well tested configurations of these applications. More often than not, the IT stack applications and configurations heavily depend on the underlying Android Stack. That means it pays to support these applications and configurations on a limited set of latest versions of Android.

When it comes to the upgrades (read patching) of the Android stack, both the carrier and vendor have long release cycles in place for stack upgrades on target devices. As a result, most smart phones that are more than a year old end up running Android versions that are old and probably not patched fast enough. This is true with any mobile OS though, not just with Android.

Supporting the IT Stack in the above picture is a nightmare for IT staff if they are to support this on multiple and older versions of mobile operating systems. Due to this, the IT staff may want the mobile phones to run with the latest OS. But the large release cycles of phone vendors and carriers often become a hurdle to accomplish this.

Android One (https://www.android.com/one/) is the best solution out of that version control mess. I have been using a cost effective and reasonably powered Android One phone since 2014. Over the last year and half, this phone has become my device of choice for use cases that strictly require latest versions of Android Platform and its eco system. The use cases include IT tools like VPN connectivity apps, single sign-on solutions, device control/erase solutions, messaging solutions and sharing solutions. This $100 unlocked dual SIM phone is a very reasonable investment for accomplishing adherence to stringent IT policies.

Android One is supported by phones that are very high end (e.g. the Nexus series sold directly by Google) all the way to cost effective phones in emerging economies. In almost all cases, the phones come with unlocked versions, leaving a wider choice of carriers to customers.

Updates to my Android One smartphone have been regular and painless in the last year and half. The ability to grab the latest update of Android within a few hours makes Android One my preferred choice.

In any BYOD centered IT infrastructure, Android One is the best way to go for IT staff to enforce tighter IT policies on smart phones while ensuring that the user devices are running with latest version of the mobile stack. That in turn ensures that the IT stack on the smartphone is current and easy to manage.

Identity as the Perimeter

03 Sep

Raju Alluri 0 Comment Security, Technical

The perimeter of an enterprise has been its LAN and WAN for quite a number of years. The popularity of VPN based remote access did extend the definition of an enterprise’s perimeter to the remote presence of its employees, albeit for short bursts of time more often than not.

As trends like Cloud based services and BYOD emerged, enterprises have this daunting challenge of protecting their data. In the new age network, data gets hosted (e.g. public cloud services) and accessed (e.g. laptops and phones) on devices that are beyond the firewalls of an enterprise. Moreover, employees want more and more flexibility towards accessing data – at wherever they are and on whatever they carry.

RSA‘s Jason wrote this blog post in which he describes the (potentially outdated) strategy of one of the Information Security persons he met – take out access to anything that has a hint of risk. Jason identifies the problem as well as side effects of that approach.

Here are the key assumptions enterprises need to make regarding their data:

Data takes multiple forms: e.g. Email, documents, code, tools, configurations and employee personal data
Each form of data might need different levels of access in terms of confidentiality and integrity: e.g. read-only, read-write for owner, write-once, privileged read-only and limited access
Data gets hosted at multiple locations (often beyond the firewalls of the enterprise): e.g. E-mail service provider, private data centers, private clouds, shared public clouds
Data gets accessed from multiple locations (often beyond the firewalls of the enterprise): e.g. desktops, laptops, phones, and to take it a step forward, TVs and car infotainment systems capable of reading your email.

Centrify‘s Tom Kemp shares his thoughts on making identity as the new perimeter. Making identity as the new perimeter has potential to provide solutions to many of the challenges arising out of the assumptions we listed above for the enterprise.

Identity controlled by an enterprise can be made to control access to data that takes different forms.
Enterprises can use single sign on (SSO) solutions that go beyond two factor authentication to provide on-demand access to data using identity as the primary factor
SSO solutions make it easy for the enterprises to control identity driven access consistently across multiple service providers like public clouds, internal data centers, private clouds.
SSO solutions, combined with device remote access/control solutions make it easy for enterprises to control the life of data persisted on nomadic devices like phones. This helps when a device is no longer tied to the same identity.

There is lot of mindshare building around managing identity and making it as a primary factor in access management. As Jason observes in his article, identity should be managed well beyond making it a two factor authentication. Context should be clubbed with identity to make more meaningful decisions for giving access to privileged information. That requires wiring several identity management and analytics products together for dynamically determining access levels.

Google already does this for its own services. If you login from a unusual location, device and application, it has the ability to enforce additional steps in determining the identity. I am really impressed (but not at all surprised) by Google’s ability to take it to not just the location and device level, but also application level. For example, Google maintains analytics data about your favorite browser on your desktop for accessing drive and if you change it, it notifies (and often counters you with additional checks, depending on context) you about that change.

I take Google’s approach as an exemplary first step in driving the identity with augmented data around context. As identity management solutions evolve, enterprises can bank on independent and collaborating solutions that determine identity. The collaboration among these solutions would be around determining the context of the user and making decisions around whether the identity can be determined unambiguously within that context. As the definition of perimeter evolves to center more around identity, these emerging trends in identity management are both welcome and necessary.

Availability is a fundamental requirement of Security

11 Jun

Raju Alluri 0 Comment Brain Dump, Security, Technical

When people talk about security, they often picture confidentiality and integrity in their mind. However, the role of availability is equally important while defining the security. In fact, the term security is defined as a combination of confidentiality, integrity and availability by major standards and certifications.

There is a quote on a lighter tone in security community: The most secure computer may be the one that is not connected to any network. But such systems hardly play any major role in providing meaningful services to customers and consumers. The goal of a security expert is to ensure that the system (and its services) are available to all the intended users, while preserving the confidentiality and integrity of the data, system and its services.

For an end user facing service (say, a shopping site or a cloud service) to operate as expected, it requires several internal or public facing infrastructure services to operate in tandem. A shopping site might require its DNS service (public), CDN service (public) payment exchange (public) and private cloud service (internal) to function properly for delivering its online services to end customers. As the comprehensiveness of online services increase, there are more and more micro-services, infrastructure services and housekeeping services that play a major role in determining the health and availability of the overarching (end user facing) service.

As big companies increasinglyÂ outsource their IT infrastructure to cloud service vendors (DNS, mail, compute infrastructure, to name a few), they increasingly depend on availability of each of these infrastructure components. As cloud service providers mature their infrastructure services, they become more and more alluring to small enterprises and startup companies, given the lower entry cost and least effort to scale up. In a nutshell, the availability of services outside the perimeter of a company, irrespective of its size, becomes essential element in offering secure services to the employees and customers of that company. On a side node, the definition of the perimeter of a company is fast diluting with more and more cloud service providers offering infrastructure services.

Even for companies that internally host their infrastructure services, the availability of these services is the most critical component in providing secure services to their end customers or employees.

Lack of availability of contributing components severely impacts security of an online service. Lets take a look at a simple example. When an authentication and authorization component operates at lesser availability levels, users of that component (developers, IT admins) make amends to lessen the impact of non-availability. For example, they may want to cache a few things for a longer amount of time. That makes any online service that depends on that authentication and authorization mechanism more vulnerable than a service that operates on top of a highly available authentication and authorization service. As more and more amends are made to reduce the impact of availability of internal components, the online service gets more holes in its security.

Every developer and IT engineer should work towards providing hooks for availability metrics and augmenting them with actionable operating procedures when availability gets impacted. These hooks and procedures should be fine-tuned as time goes on and as new factors influence the availability.

Every security expert should look at availability of an online service and that of its internal components as fundamental requirement for ensuring security of such service. Ample bells and whistles (in the form of monitoring and management infrastructure) should be setup to catch availability issues within an online service’s eco-system. Trends related to lesser availability of a component and service need to be detected and acted up on.

authbind vs iptables on AWS

29 Jan

Raju Alluri 1 Comment Security, Technical, Unix/Linux

Here is a short description of the scenario I was working on. I am using a standard AWS AMI to run tomcat (tomcat7, to be specific.) The default configuration of AWS AMIs (and many other off-the-shelf unix based servers) is such that tomcat (or any other program that runs with a non-superuser credentials) can’t bind to privileged ports. However, tomcat needs to use these privileged ports (443 for TLS and 80 for standard HTTP) to serve public facing pages.

Making tomcat run as superuser is really a bad idea (the why question is beyond this article.) So there are a few tricks to make tomcat work on privileged ports.

authbind

There is lot of mindshare around authbind when it comes to hosted environments. The manpage of authbind describes how authbind can be used to make a program bind to sockets on privileged ports. However, if you are using a standard AWS AMI, you may have some challenges using authbind. Also, for automated environments (read Chef) in AWS, I felt authbind is more complicated to work with.

iptables

Port redirection using NAT features of iptables is very simple and straight forward. However, it requires an additional configuration on tomcat to use proxy mode on privileged ports.

Here is the NAT configuration using iptables.

sudo /sbin/iptables -t nat -I PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080
sudo /sbin/iptables -t nat -I PREROUTING -p tcp --dport 443 -j REDIRECT --to-port 8443
sudo service iptables save

Once this is done, all inbound traffic on 80 will be redirected to 8080. The same is the case with port pair 8443 and 443. This way, tomcat can still bind to port 8080 for HTTP and 8443 for TLS while serving incoming connections on 80 and 443 respectively.

When a client program queries the port information from tomcat, it should respond with port 80 and 443 instead of 8080 and 8443. To ensure that, one can use the proxy support feature of tomcat. Here is the additional configuration in tomcat connector settings in server.xml

<Connector port="8443" proxyPort="443" .../>
<Connector port="8080" proxyPort="80" .../>

Other Considerations

There are better ways to handle this port redirection when you have front-ending loadbalancers and/or proxy servers in place. Having proxy/loadbalancers solves helps mitigate more issues than just solving the redirection problems. However, the iptables approach is better than authbind approach when you are using a single server on AWS without lot of additional infrastructure and configurations in place.

Data Insurance: to Limelight and Mainstream

31 Dec

Raju Alluri 0 Comment Brain Dump, Economy, Security, Technical

In contrast with other essential elements of human life like death and taxes, the history of insurance has been very short. However, in terms of evolution, the concept of insurance has been constantly changing and continuously embracing new domains. Insurance of properties, life, health, beauty, athletic talent and limbs are very trivial now. Data insurance, which has been limited once to multi-billion dollar corporates and that too for limited scenarios, is now taking center stage.

The drivers for data insurance existed for quite some time, but they haven’t proliferated into human life and organizational practices as it happens now. The key drivers pushing the trend towards data insurance are the protections we need against data loss, data compromise and data misuse.

Organizations, as they evolve in their presence over web, social networks and mobile applications, are capturing more and more data. The rest of the discussion in this article focuses on two categories of this data.

Acquired data: All the customer information, employee information and any other user information collected directly or indirectly from the users constitutes this acquired data. By nature, this class of data is highly likely to have sensitive information that includes personally identifiable information (PII), credit card information, etc.
Generated data: All the housekeeping, analytics and user behavior data in an organization falls into this category. This data is very vital in deliveringÂ better user experience to both end users and internal teams. This data is mostly generated by an organization’s web/mobile applications that interface with end users and may be augmented with data inferred from other user interactions like support calls and email exchanges.

Any compromise on acquired data leads to a very big exposure – loss of face, legal tangles and/or customer loyalty issues. The data compromises detected at companies like Target and Home Depot are leading to customer unrest, loss of loyalty and severe financial implications from legal consequences.

Any compromise of generated data makes an organization limp (often heavily) in their business process. Generated data compromise mostly leads to inefficiencies and exposure of the secret sauces to competition.

The impact of a compromise on generatedÂ can’t be taken any lightly when compared to the impact of acquired data compromise. The generated data may also include intellectual property related items that could hurt a company in the long run when that data is compromised.

Digital (or digitized) data captured by humans also is increasing in its prominence,Â value and the risk of compromise. Whether it is personal pictures of celebrities or tax data of individuals, the risk associated with any compromise of this data is increasing over time. As the data access avenues are increasing (e.g. health data accessed via a wearable device), the potential for compromise of personal data is also increasing.

Given all this increased focus on data and its risks, we see a bigger shift towards insuring the data by corporations and individuals. Data Insurance is taking new paths that are less traveled by insurance companies in the past. Data Insurance packages now contain and cover a wide variety of data sets.

Just like humans undergo a set of prerequisite tests before taking a new health insurance package, data sets might undergo certain audits that cover the access controls and security risks associated with this data. We may also see a trend towards re-audits during renewals of data insurance to re-validate the access controls and risks.

The key factor in Data Insurance is determining the value of data. Human life insurance packages usually cover sums like 5x annual income. Vehicle insurances usually cover up to the Bluebook value of a vehicle. Coming up with valuation for data is not that straight forward though. The valuation process might differ greatly between acquired data and generated data. Unlike constant depreciation of a vehicle’s Bluebook value, the value of data may either decrease (data that becomes stale over time) or increase (with volumes or with increased sensitivity of same data) over time. Data Insurance companies and the insured organizations/individuals will often be re-evaluating the value of data to optimize costs and minimize the impact of exposure.

In summary, here are some of the primary factors by which data insurance evolves:

Categorization of data
Valuation of data
Data audits

As data insurance hits mainstream, all these factors experience market growth and some sort of standardization beyond what we have today.

libressl

04 Nov

Raju Alluri 0 Comment Other Opensource, Security, Technical

Libressl (http://www.libressl.org/) is a recent fork of OpenSSL. The goal of libressl is to provide a more secure alternative to openssl and the developers who forked the code feel that openssl is beyond repair at this point. Quoting from libressl website,

LibreSSL is a version of the TLS/crypto stack forked from OpenSSL in 2014, with goals of modernizing the codebase, improving security, and applying best practice development processes.

The best documentation of libressl features (or default configurations) can be found in the release notes from 5.6 version of OpenBSD. Looking at the list, this is an impressive push towards securing the implementation by default. Without worrying too much about the backward compatibility, some of the lesser secure configurations and protocols are simply left out from the implementation.

By dropping support for a bunch of hardware engines and platforms, libressl probably has less things to worry about. For example, dropping support for big-endian i386 and amd64 systems liberates it a bit. With classic adopters of big-endian architectures evenutally becoming bi-endian, there is not much to lose here, in my opinion. However, reusing the standard C library routines like malloc() and snprintf() could take an interesting turn. Dropping kerberos support is interesting too – don’t we still have a lot of academic community working on it?

I like changes like dropping SSLv2 support and stopping the use of current time as random seed among a few others.

There are several discussions in the past on which of these opensource SSL implementations are better. Being a legacy implementation, OpenSSL at this time requires a considerable set of configurations to make it secure. From that view point, libressl might look better in terms of its out of the box readiness for a more secure implementation. However, in the world of automated deployments and continuous integrations, recipes exist to configure openssl to avoid less secure protocols and algorithms.

I am not sure at this point whether libressl will surpass openssl in future in terms of adoption, but sure I am glad to see a drive towards being “more secure by default.”

Shellshock bug and the risks

26 Sep

Raju Alluri 0 Comment Cloud, Security, Technical, Unix/Linux

Bash, the quarter century old shell utility on almost all popular unix based systems, is found to be vulnerable. The exploit works by injecting specially crafted values into an environment variable and using it to invoke a shell command. Once the exploit gets to that level, there is hardly any limit on what can be executed as part of the shell command.

The problem gets worse for the fact that many of the day to day usages of the network facing services have potential to use bash internally. For example, CGI scripts on web servers, convenience utilities offered by network routers and any other limited command execution tools might be the key vulnerability public and guest access private networks. Mitre warns that sshd with ForceCommand is a potential attack vector.

The bug is being termed as Shellshock bug or bash bug. RedHat’s security blog article is one of the earliest articles that discussed the Shellshock bug in detail. Robert Graham of Errata Security is the best known tracker of the issue and has ongoing observations and comments on his blog/twitter account.

Here is how you can check if the current bash is vulnerable on your system. If it prints vulnerable on the first line, then patch your bash package.

$ env x='() { :;}; echo vulnerable' bash -c "echo test completed"
 vulnerable
 test completed

For web servers, here is the test suggested:

$ curl -i -X HEAD "http://sometestdomainhere.com/" -A '() { :;}; echo "Warning: Server Vulnerable"'

The output looks somewhat like the following listing. If it contains “Warning” text, then it is highly likely that the web server’s bash is (and cgi’s based on bash are) vulnerable. This test doesn’t assure that the system is not vulnerable. You may still have other CGIs run with bash that are vulnerable.

HTTP/1.1 200 OK
Date: Fri, 26 Sep 2014 02:51:52 GMT
Server: Apache
X-Powered-By: PHP/5.4.32
X-Pingback: http://sometestdomainhere.com/xmlrpc.php
Link: <http://sometestdomainhere.com/?p=14>; rel=shortlink
Content-Type: text/html; charset=UTF-8

Since the Shellshock bug existed for quite a while, all versions of bash that are currently out there in active usage are likely to be vulnerable. Patching some of these devices might be trivial, but there still might be several other devices that are hard to patch.

Servers that run services like web/ftp might be vulnerable if the CGI scripts end up using bash. Invoking bash from PHP code is considered not vulnerable, unless there are ways to circumvent input parameter validations of the PHP code. The RedHat article mentioned above has links to instructions on how to fix this on RedHat variants of linux. For Ubuntu, this is a good thread to follow.
Desktops that use network facing services like DHCP over wireless and sshd are vulnerable as long as these services internally use bash commands or bash as the shell for the session. There are still discussions on whether Mac OS X DHCP is vulnerable or not, because Apple modified its DHCP and claims that the DHCP utilities don’t use bash internally. Mac OS X branched version 3 of bash and does its own updates to the shell. There are instructions on how to patch OS X, tailored more for unix admins (and requires xcode) than normal users.
There are some suggestions on renaming bash to a different name, but that might break more things than fixing them. Use this technique with utmost caution.
Â Beyond Desktops and Servers, devices like internet routers may have vulnerabilities due to utilities and services they offer. For these devices, waiting for vendor released patches is the best option, but explore the possibility of turning off these convenience utilities.

Errata Security also has notes on wormable nature of the Shellshock bug. So patch your bash package as early as you can.

Upcoming AWS / EC2 instance reboot

25 Sep

Raju Alluri 0 Comment Cloud, Security, Technical, Unix/Linux

If you are using AWS and EC2 instances, a reboot of most those instances is on the horizon. Amazon’s AWS informed of this reboot that is scheduled between 02:00 GMT on September 26th and 23:59 GMT on September 30th.

Read more about this reboot on Gigaom and Rightscale. Technical Forums on AWS and other sites are already buzzing with lot of traffic, discussing the potential impact and how to ensure that the services are not impacted.

Given the urgency and magnitude of the instances that are impacted, it looks like the patch is going potentially going to address a security vulnerability. The actual details of the patch and the issues that are fixed by it will be known around October 01st.

Summarizing various discussions on related forums, here is a quick summary of what to watch out for during this AWS / EC2 instance reboot

The reboot is not limited to any single availability zone. It spawns across all the availability zones
Good news is that the EC2 instances on all availability zones are not rebooted at the same time. So if your instances spawn across multiple availability zones, you are on a relatively safer side.
The reboot does not impact instances of the type T1, T2, M2, R3, and HS1. However, if the patch fixes issues on these instance types too, then you might be on your own. We will know more around October 1st.

Here are a few quick checks for those who are getting impacted.

Check your mailbox for a notice from AWS and it is likely to give more details about the reboots, impact and schedules
Ensure that the key services on your instances are configured for auto restart when the system boots up. It looks silly, but I have seen code that takes good care of newly spawned instances but doesn’t address reboots that well.
Ensure that your network paths (non-Elastic IPs, Route 53 entries, S3 buckets) survive reboot of the instances.
For those whose instances are NOT rebooted by AWS, watch out for the issues fixed by AWS during this reboot and evaluate their impact on your instances. Take corrective measures as soon as possible.

For those who can afford to be heroic enough – why wait till AWS reboots your instances? Reboot these on your own in each availability zone and test the resilience.

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Category: Security

authbind

iptables

Other Considerations