Author: Ryan MacDonald

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(ATF) Aggregate Threat Feed

aggregate feed sexyness
ATF sexyness

For my first post back into things in awhile (a long while), I thought I would introduce everyone to the sexyness that i’ve called the Aggregate Threat Feed or ATF for short. This feed is derived from threat data at work, namely our network edge IPS (a custom snort implementation, another post on that later) and aggregated firewall data from 250+ servers, mostly being brute force/invasive scan attack addresses.

There really is nothing terribly fancy about this, the data is presented in a drop list format that is updated every 15 minutes with an optional variable to adjust the amount of addresses returned:

http://asonoc.com/api/atf.php?top=50 (defaults at 100)

The entries in the list are sorted on the database side by highest event count first, you can optionally view the source and event count entries in the list but this is considered strictly for review purposes (it wouldn’t be of much other use). Take note that the maximum value for ‘top’ is 300.

http://asonoc.com/api/atf.php?top=300&fmt=list

The review data looks something like follows:

IP | SOURCE | EVENTS
———————-
187.45.224.5 ips 227
92.48.206.91 ips 202
69.13.196.47 fw 176
210.17.251.159 ips 130
83.170.110.194 fw 125

This is pretty basic to understand, the distinction to note however is that event numbers for IPS source data can be 50 events against 1 or 20 servers whereas the event count for fw sourced data typically reflect unique servers. So an address sourced from fw data with 200 events, actually hit 200 servers.

The next release of APF due in the coming months, will feature many changes and among them will be the inclusion of ATF as part of the new feed subscription feature. Further, users will have the option to enable reporting to the rfxn.com server that allows your own block data to be included in the ATF database. As more installations opt-in on this feature it will allow data aggregation to reflect a more global threat landscape that truly represents the users of APF (currently active installations based on those fetching the rfxn.com reserved.networks list daily: 46,921).

Also on the agenda is a simple ATF landing page that presents statistical data and some fancy graphs/charts (probably use google api cause im lazy like that), that will allow users to better visualize threats included in the feed and details on the actual events that caused an address to end up in it (snort events, firewall triggers etc..).

EOF

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Upgrade CentOS 4.8 to 5.x (32bit)

Traditionally, the dist upgrade path that many were familiar with from the RH8/9->Fedora or similarly Fedora dist upgrades, have applied more or less to RHEL/CentOS but with the release of 4.5 and early releases of 5.0 the actual dist upgrade path was messy or nearly impossible. The early versions of 5.0 (up to 5.2) had excessive dependency issues with versions later than 4.4 for straight dist upgrades that would often result in a box blowing up on you or forcing a messy downgrade attempt of 4.5+ to 4.4 to try get things to dist upgrade. With more recent release updates the gap has closed and now dist upgrades on are far more reasonable to complete with little in the way of problems.

If you are currently running a version of RHEL/CentOS earlier than 4.8 (cat /etc/redhat-release) then please do a proper ‘yum update’ and get yourself on 4.8. Although this is intended for CentOS it “should” (read: at own risk) work on RHEL systems as well, in the unfortunate situation that something does blow up please post a comment and I will try to assist.

The first thing we must do is make sure none of our core binaries, libraries or other content is set immutable as this will cause a package to fail on installation. If you are running an earlier version of LES or you use immutable bits on system paths (sbin/bin/share/include/libexec/etc) then you should run the following:

wget http://www.rfxn.com/downloads/disable.les.rpmpkg
sh disable.les.rpmpkg

Once that is done we should go ahead and have a quick run through of cleaning up yum cache, double check that any pending updates are installed and rebuild the rpmdb:

rpm --rebuilddb
yum clean all
yum update

If for some reason the rpm rebuild hangs for more than a few minutes then you may need to manually clear the rpmdb files:

rm -f /var/lib/rpm/__db.00*
rpm --rebuilddb

If you run into any minor dependency issues for packages that are not essential, such as syslinux and lftp then you can either exclude them or better yet remove them. If you are not sure what a package does, then you should query it for description details and make an educated choice (rpm -qi PACKAGE):

rpm -e lftp syslinux mkbootdisk

OR (but not recommended)

yum update --exclude=syslinux --exclude=lftp --exclude=mkboot

At this point you should be able to run a ‘yum update’ command with optional exclude and receive no errors (again, I recommend you remove conflicts items instead of using exclusions).

# yum update –exclude=nagios-plugins
Setting up Update Process
Setting up repositories
Reading repository metadata in from local files
Excluding Packages in global exclude list
Finished
No Packages marked for Update/Obsoletion

Now we are ready to get going, I have put together a small package that contains the needed packages for this upgrade in addition to a few that you might require to resolve dependency conflicts:

wget http://www.rfxn.com/downloads/CentOS-5up.tar.gz
tar xvfz CentOS-5up.tar.gz
cd CentOS-5up

We need to go ahead and setup the centos-release package as follows:

rpm -Uhv centos-release-*

If you see that CentOS-Base.repo was created as /etc/yum.repos.d/CentOS-Base.repo.rpmnew then go ahead and move it into the proper place:

mv /etc/yum.repos.d/CentOS-Base.repo.rpmnew /etc/yum.repos.d/CentOS-Base.repo

Now we are ready to go with kernel changes, this is an important part so pay attention. The key to successful upgrade is that you remove ALL OLD KERNELS as many packages will fail to install during the upgrade if they detect a release 4.x kernel due to minimum kernel version dependency checks. We will start with first installing the new kernel so it preserves grub templating:

rpm -ivh kernel-2.6.18-164.el5.i686.rpm kernel-devel-2.6.18-164.el5.i686.rpm --nodeps

NOTE: release 5.x has smp support integrated into the standard kernel, so no -smp version is required for mp systems

If you are running an older system the chances are you got allot of older kernel packages installed so make sure you get them all out of the way:

rpm -e $(rpm -qa | grep kernel | grep -v 2.6.18 | tr '\n' ' ')

You may end up with a few dependencies coming up such as lm_sensors and net-snmp if the list is fairly small and packages you do not recognize as critical (if unsure always query the package for info ‘rpm -qi PACKAGE’, remember you can reinstall them later):

# rpm -e $(rpm -qa | grep kernel | grep -v 2.6.18)
error: Failed dependencies:
kernel-utils is needed by (installed) lm_sensors-2.8.7-2.40.5.i386

The command the ended up being required on most of my servers to get the kernel packages and related dependencies came out to the following:

rpm -e $(rpm -qa | grep kernel | grep -v 2.6.18 | tr '\n' ' ') lm_sensors net-snmp net-snmp-devel net-snmp-utils

That said and done you should now only have 2 kernel packages installed which are the 2.6.18 release 5.x kernels, DO NOT under any circumstance continue if you still got 2.6.9 release 4.x kernels packages still installed, remove them!

# rpm -qa | grep -i kernel
kernel-2.6.18-164.el5
kernel-devel-2.6.18-164.el5

A cleanup of /etc/grub.conf may be required, though if all went as planned then the rpm command should have done this up for us but review it anyways for good measure. You should find that 2.6.18-164.el5 is the only kernel in the file, if it is not go ahead and clean it by removing all older entries for 2.6.9 kernels.

There is a known bug with python-elementtree package versions which cause yum/rpm to think the release 4.x version is newer than the 5.x version, to get around this without blowing up the entire python installation we need to remove the package from just the rpmdb as follows:

rpm -e --justdb python-elementtree --nodeps

We can now go ahead and use yum to start the upgrade process, this is a dry run and will take a few minutes to compile list of available packages and associated dependency checks. You should carry the exclude options, if any, that you used during the ‘yum update’ process as so to avoid unresolvable dependencies:

yum clean all
yum upgrade --exclude=nagios-plugins

You will end up with a small list of dependency errors, these should be resolved by again evaluating a packages need as a critical system component and either removing it with ‘rpm -e’ or excluding it with ‘–exclude’ (remember to query description with ‘rpm -qi PACKAGE’ if you are unsure what something does). In my case the packages that threw up red flags were stuff I had manually installed over time such as iftop and mrtg in addition to default installed samba, these can all safely be removed or excluded as you prefer (removal always safest to prevent dependency chain issues).

Error: Missing Dependency: libpcap.so.0.8.3 is needed by package iftop
Error: Missing Dependency: perl(Convert::ASN1) is needed by package samba
Error: Missing Dependency: libevent-1.1a.so.1 is needed bypackage nfs-utils
Error: Missing Dependency: perl-Socket6 is needed by package mrtg
Error: Missing Dependency: perl-IO-Socket-INET6 is needed by package mrtg


rpm -e iftop samba nfs-utils mrtg system-config-samba

At this point we should be ready to do a final dry run of with yum and see where we stand on dependencies, rerun the earlier ‘yum upgrade’ while making sure to carry over any exclude options you are using.

yum upgrade --exclude=nagios-plugins

You should now end up with a summary of actions that yum needs to perform, go ahead and kick it off… this will take a bit to complete so go grab some coffee/jolt/redbull and maybe a small snack cause it could be a long night if this blows up on you.

Transaction Summary
=============================================================================
Install 183 Package(s)
Update 327 Package(s)
Remove 0 Package(s)
Total download size: 299 M
Is this ok [y/N]:

Once yum has completed (hopefully without major errors) we need to fix a few things, the first is the rpmdb needs a rebuild due to version changes that will cause any rpm commands to fail:

# rpm -qa
rpmdb: Program version 4.3 doesn’t match environment version
error: db4 error(-30974) from dbenv->open: DB_VERSION_MISMATCH: Database environment version mismatch
error: cannot open Packages index using db3 – (-30974)
error: cannot open Packages database in /var/lib/rpm

This can be fixed by running the following to manually rebuild the rpmdb:

rm -f /var/lib/rpm/__db.00*
rpm --rebuilddb
yum clean all

The next issue on the list is python-elementtree and python-sqlite, one or both of these may have ended up in a broken state that will cause all yum commands to break, so we will go ahead and reinstall both of these for good measure:

rpm -e --justdb python-elementtree --nodeps
rpm -ivh python-elementtree-1.2.6-5.el5.i386.rpm
rpm -ivh python-sqlite-1.1.7-1.2.1.i386.rpm --nodeps --force

The yum command should now work, go ahead and run it with no options, if you do not get any errors you are all sorted.

Hopefully the install went well for you, the only thing left to do is go ahead and reboot the system; this is the last point at which you have to make backups (but we all maintain backups right?). For the sake of avoiding a heart attack if the system goes into an fsck, we will reboot with the -f option to skip fsck:

shutdown -rf now

That’s a wrap, I hope you found this HowTo useful, if you did run into any issues then go ahead and post them into the comments field and I will try to assist but when in doubt typically google is the fastest alternative.

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Linux Malware Detectection

[ UPDATE: Linux Malware Detect has been released ]
I have the last few weeks been working on a new project for malware detection on Linux web servers, it is already at a pre-release version in use at work and it has shown phenomenal promise.

Right to it, some background… On a daily basis the network I manage receives a large number of attacks, most of these are web based abuses against common web application vulnerabilities which inject/upload to servers an array of malware such as phishing content, defacement tools, exploits for privilege escalation and irc c&c bots. All these actions are typically logged and recorded by our network edge snort setup which got me to thinking if we started to catalog some of the injected malware, I could hash it and then detect it on servers.

Now, some might be thinking – “network edge IDS? why not convert it to IPS and stop the attacks right away?” – though this is something I am actually in the process of doing, there is a much larger problem and that is content encoding. Allot of malware attacks are coming in these days in base64 and gzip encoded data payloads which snort or any other IDS/IPS products for that matter are currently NOT capable of decoding without use of fancy transparent proxy setups that are out of the scope of standard network edge intrusion detection/prevention.

So, this brings us to a host based solution for malware detection which as it turns out is not so easy as there is no simple sites that actually track malware specifically targeting web applications and the ones that do exist focus primarily on Windows based malware; utterly useless. To address this short coming, what I have done is essentially written a set of tools that extracts from specific ids events the payload data of attacks (decodes if needed) and saves/downloads the content attackers are trying to inject. This data is then processed for false positives by me every couple of days followed by the creation of md5 hashed definitions of the malware for the detection tool. The hashes are compiled in two methods, the first is straight md5 hashes of the data and the second are hashes of “chunked” elements of the data in specific increments and formats as so to detect commonly occurring malware code in otherwise unique files and content types.

The scanner portion of the malware detection tool comes in 3 varieties, the first is a standard “scan all” feature which scans an entire defined path, the second is a “scan recent” feature that can scan a path for content created in the last X days (i.e: /home/*/public_html content created in the last 7 days) and the third is a real time monitoring service component that uses Linux inotify() kernel feature to detect real time file create/move/modify operations and scan content immediately as it is created under user web paths (default /home[2]/user/public_html).

The malware hit management is a very simple anti-virus like quarantine system that moves offending files to ‘INSTALL_PATH/quarantine/’ and logs the exact source path and destination file name in quarantine locker in case you need to restore any data due to false positives (though this should never happen since we are using hashed detection). In addition, the quarantine function can optionally search the process table for running tasks that contain the file name of the offending malware and kicks off a kill -9 against it.

The event management is handled in two ways, for manual user invoked scans from cron/command line, emails are directly dispatched with the scan results including quarantine details – nothing really fancy here. The monitor component that uses inotify() on the other hand, has the potential to generate allot of quarantine events in rapid succession so a standard email out on every hit isn’t appropriate. Instead, we have a daily cron job that runs an internal option in the malware detect tool to read ONLY new lines from a quarantine hit list and dispatch a daily event summary if any quarantine hits are found. Since we are only reading new lines from the hit list, we avoid repetitive daily alerts for events we already know about and retain the hit list as an “all-time” hit list that can later be used to derive trending data / phone home features for global trending.

Finally, the project also contains an internal update function to check for new hashes and runs in the daily cron task in addition to a simple check feature that determines if inotify() based monitoring is running, if it is not then it kicks off against /home[2]/user/public_html a scan for content created in the last 48h.

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The Way Forward

It is hard to believe the year is almost done and gone already, it has been busy for me with some life drama earlier in the year then a couple of larger projects keeping me on my toes since then.

During the last few weeks I have taken the time to draft a solid road map for the projects and where I would like them to be by this time next year. The road map evolved in very organic fashion with me jotting down a few points here and there every day, now it is pretty long but very constructive. It is not really something formal enough for me to release in its retarded disorganized point-form fashion but I will touch on a few items.

The biggest community oriented change will be bringing the projects source to a svn/git management system with the usual web interfaces to go with them and allow public bug/contrib additions/tracking. This to some might seem like a really long overdue task but you need to understand that the projects to this point have been developed to cater to my administrative needs day-to-day with work and secondary to the community. Although I will still put priority on features I require, it will become easier for others to submit contributions and assist with bug tracking, hopefully allowing for a more robust set of projects in the end.

The next big ticket item on the road map is the integration of projects into a suite utility which is a long standing desire of mine and others but it requires allot of work. I have decided that it is best to just completely rewrite many of the projects instead of trying to hack them into some half-ass suite utility. The age of APF and BFD is beginning to show, they no longer really compete with some other tools and in certain cases even find themselves dragging behind in performance, features and usability. I intend to modernize the projects by rewriting them in cleaner (read: documented) code with clear project targets that are better outlined from the start along with features that will blow other Linux firewall wrappers and security suites out of the water. I do not want to get into the actual gritty details of specific plans yet but things are definitely going to change in a good way.

On smaller items there is about 40 odd specific items I have put down to paper, that range from feature additions, enhancements, rewrites, bug fixes and contrib additions that need to be worked on either in conjunction with the suite project or before it can even get off the ground. Though these are tedious tasks they are all things that must be done and will get done, I will detail further on these actual items in a future post but for now it is only important to keep in mind that the suite will not beat around the deficiencies of the smaller projects, everything will get some TLC.

I know this post is not that forthcoming in specifics but stay tuned, I will get the road map cleaned up and posted soon. One of the new projects that will become part of the suite will be a malware detection utility primarily for web servers which you can read more about here.

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Snorting the Web Farm

Here are some rules for you snort freaks to chew on that I have found useful in web heavy environments.

alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE x2300 phpshell detected"; content:"Locus7Shell"; nocase; classtype:web-application-activity; reference:url,www.rfxn.com; sid:300010; rev:1;)
alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE RFI Scanner detected"; content:"RFI Scanner"; classtype:web-application-activity; reference:url,www.rfxn.com; sid:300020; rev:2;)
alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE lila.jpg phpshell detected"; content:"CMD PHP"; classtype:web-application-activity; reference:url,www.rfxn.com; sid:300030; rev:2;)
alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE ALBANIA id.php detected"; content:"UNITED ALBANIANS aka ALBOSS PARADISE"; classtype:web-application-activity; reference:url,www.rfxn.com; sid:300040; rev:2;)

alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE Data Cha0s Backdoor"; content:"Data Cha0s Connect Back Backdoor"; classtype:web-application-activity; reference:url,www.rfxn.com; sid:300050; rev:1;)
alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE Data Cha0s Backdoor"; content:"Spawning Shell"; classtype:web-application-activity; reference:url,www.rfxn.com; sid:300051; rev:1;)

alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE c99 phpshell variant"; content:"c999shell v."; classtype:web-application-activity; reference:url,www.rfxn.com; sid:300060; rev:1;)
alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE c99 phpshell variant"; content:"C99 Modified"; classtype:web-application-activity; reference:url,www.rfxn.com; sid:300061; rev:1;)
alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE c99 phpshell variant"; content:"RootShell Security Group"; classtype:web-application-activity; reference:url,www.rfxn.com; sid:300062; rev:1;)
alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE c99 phpshell variant"; content:"Modded by Shadow & Preddy"; classtype:web-application-activity; reference:url,www.rfxn.com; sid:300063; rev:1;)

alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE js insert redirect"; content:"META HTTP-EQUIV='Refresh' CONTENT='0"; nocase; content:"text/javascript"; nocase; pcre:"/daobrains\.info|engaolika\.info|globalsecurityscans\.com|goscanpark\.com|goscansome\.com|goscansoon\.com|goslimscan\.com|neborin\.info|safetyshareonline\.com|securityexamineonline\.com/i"; classtype:web-application-activity; reference:url,blog.unmaskparasites.com/2009/07/23/goscanpark-13-facts-about-malicious-server-wide-meta-redirects/; sid:300070; rev:3;)

alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE DarkMailer"; uricontent:"cgi"; nocase; uricontent:"m="; nocase;  pcre:"/dark\.cgi|dm\.cgi|da\.cgi/iU"; classtype: web-application-attack; sid: 300080; rev:1;)
alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE DarkMailer"; content:"yellsoft"; nocase; content:"DirectMailer v"; nocase; classtype: web-application-attack; sid: 300081; rev:1;)

alert tcp $HTTP_SERVERS $HTTP_PORTS -> any any (msg:"ET ATTACK RESPONSE r57 phpshell footer detected"; content:"http-shell by RST/GHC"; classtype:web-application-activity; reference:url,www.pestpatrol.com/spywarecenter/pest.aspx?id=453096755; sid:2003535; rev:4;)
alert tcp any any -> $HTTP_SERVERS $HTTP_PORTS (msg:"ET ATTACK RESPONSE r57 phpshell source being uploaded"; content:"by 1dt.w0lf"; content:"GHC http"; distance:0; classtype:web-application-activity; reference:url,www.pestpatrol.com/spywarecenter/pest.aspx?id=453096755; sid:2003536; rev:5;)

alert tcp any any -> any any (msg:"ET ATTACK RESPONSE devil_ shellbot: conback request"; content:"Conectando-se em"; classtype:attempted-admin; reference:url,www.rfxn.com; sid:300090; rev:1;)
alert tcp any any -> any any (msg:"ET ATTACK RESPONSE devil_ shellbot: udp flood"; content:"pacotando"; content:"temp"; classtype:attempted-dos; reference:url,www.rfxn.com; sid:300091; rev:1;)
alert tcp any any -> any any (msg:"ET ATTACK RESPONSE devil_ shellbot: udp flood"; content:"de envio"; content:"Total pacotes"; content:"Total bytes"; content:"Tempo"; classtype:attempted-dos; reference:url,www.rfxn.com; sid:300092; rev:1;)

alert tcp any any -> any any (msg:"ET ATTACK RESPONSE /bin/sh shell spawn"; content:"no job control in this shell"; classtype:attempted-admin; reference:url,www.rfxn.com; sid:300100; rev:1;)