R-fx Networks

LMD 1.3.9: Quietly Awesome

by on Mar.16, 2011, under Development, My Blog

It has been a busy couple of weeks for the LMD project, lots of late nights and sleepless days behind me and I can say I am a ‘little’ happier with where things are in the project now :)

This release has no major feature changes or additions other than a modification in the default hexdepth that is used to scan malware; increased from 15,736 to 61,440 (1024*60). This enables LMD to better detect threats that it was having a little difficulty with due to the byte size of some malware. At the moment there is no byte-offset feature that would allow us to create more targeted hex signatures, which kind of fly’s in the face of my goal of improving performance — but it is what it is and for the moment things are O.K. With the new hex-depth value, the miss rate on valid malware that rules already exist for is below 1% and I can live with that till I put together a new scanner engine/logic. You can apply this update to your installations by using the -d|–update-ver flags.

In light of performance concerns with the current incarnation of LMD, I felt it prudent, and also has been requested, to create a set of signatures compatible with ClamAV. This allows those who wish to do so, to leverage the LMD signature set with ClamAV’s very impressive scanner performance. Although there are performance concerns with LMD on large file sets, it does need to be said that for day-to-day operations of the cron initiated or inotify real-time scans, there is little to no performance issues. This is strictly a situation where if you choose to scan entire home directory trees, where file lists exceed tens or hundreds of thousands, you now have an option to take advantage of our signatures within a scanner engine that can handle those large file sets.

The LMD converted ClamAV signatures ship as part of the current release of LMD and are stored at /usr/local/maldetect/sigs/ and are named rfxn.ndb and rfxn.hdb. The ClamAV signatures will not be updated with the usage of -u|–update but rather are static files placed inside the release package when it is rebuilt nightly with new signatures. As such, the latest versions of the rfxn.ndb|hdb files are always available at the following URL’s (these are updated whenever LMD base signature are updated — typically daily):

To make use of these signatures in ClamAV using the clamscan command, you would run a command similar to the following:
clamscan -d /usr/local/maldetect/sigs/rfxn.ndb -d /usr/local/maldetect/sigs/rfxn.hdb -d /var/clamav/ –infected -r /path/to/scan

The -d options specify the virus databases to use, when you use the -d option it will exclusively use those databases for virus scans and ignore the default ClamAV virus database, so we redefine -d /var/clamav/ to also have all of the default ClamAV signatures included in our scans. The –infected option will only display those files that are found to be infected and the -r option is for recursive scanning (descend directory tree’s).

That all said, the real guts of changes recently have been in the signatures themselves, we have in the last two weeks went from 6,083 to 6,769 signatures, an increase of 686 — one of the largest updates to signatures to date for a single month. A great deal of these signatures have come from the submissions queue which ended up in such a backlogged state that there was 2,317 items pending review. Currently I have managed to get the queue cut down to 1,381 and I have committed myself to eliminating the backlog by the end of the month or shortly there after (ya we’ve heard that before right ?). It should be understood that reviewing the submissions queue is an exceedingly tedious task as every file needs to be manually reviewed, assessed on its merits as malware (or deleted), then ultimately hex match patterns created, classify the malware, hash it and insert it into the signatures list. As painful of a process as it is at times, I do enjoy it, it is just very time consuming so please show patience when you submit malware with the checkout option.

Finally, I have allot in store for LMD going forward, as always time is the biggest factor but be assured the project will continue to grow and improve in the best interest of detect malware on your servers. Likewise, for any who have followed previous blogs, the dailythreats website is still a work in progress and will compliment the project once it is released, in the very near future. As always, thank you to everyone who uses my work and please consider a donation whenever possible.

Did You Know? Stats:
Active Installations (Unique IP daily update queries): 5,903
Total Downloads (Project to date): 32,749
Total Malware Signatures: 6,769
rfxn.com Malware Repository: 21,569 files / 1.6G data
Tracked Malware URL’s: 18,304
Tracked IRC C&C Botnets: 421


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