Malware authors expand use of domain generation algorithms to evade detection

Domain generation algorithms are increasingly used to evade network filters and protect botnets from takedown attempts

Malware authors are increasingly adopting flexible domain generation algorithms (DGAs) in order to evade detection and prevent their botnets from being shut down by security researchers or law enforcement agencies.

DGAs are generally used as a fallback mechanism for sending instructions to infected computers when the hard-coded command and control (C&C) servers become unavailable.

The algorithms generate a list of unique pseudo-random domain names every day. Clients in a botnet attempt to connect to them and receive commands when the primary servers can't be reached.

Knowing the algorithm allows malware authors to predict which domain names infected computers will attempt to access on a certain date, so they can register one of them in advance.

The infamous Conficker worm used a domain generation algorithm for receiving instructions from its creators. This brought the technique to the public's attention for a short time in 2009.

However, DGAs have advanced considerably since then, said Gunter Ollmann, vice president of research at network security vendor Damballa. According to Ollmann, there's a trend in malware development to implement DGAs in order to evade security systems that rely on domain name reputation, blacklists or signatures.

Customizable DGA modules are now available for some of the most popular crimeware packs, such as ZeuS, which means each botnet based on them will contact its own list of domain names.

That makes it very hard to shut them down, especially for law enforcement authorities, which have little time -- around 24 hours -- to investigate a C&C server, Ollmann said.

By the time the authorities get a subpoena and take control of a temporary domain name to perform forensics, the cybercriminals will likely already have switched to a new one.

Even security vendors have had a hard time identifying the use of DGAs in certain types of malware or accounting for it when building detection, Ollmann said.

Damballa has studied DGAs for the past year and plans to present a research paper on the subject this Tuesday at the RSA Conference 2012 in San Francisco.

The company has identified six new malware families that use DGA for evasion purposes during the past 12 months. The malware families are used by dozens of cybercrime organizations.

Six additional types of DGAs have been spotted on large networks, but it's not clear what malware families are using them because samples could not be obtained from the infected clients.

The availability of the ZeuS source code on the Internet and cybercriminals' need to protect their botnets from takedowns are likely to push more malware developers to adopt DGAs in the future, Ollmann said.

Join the CSO newsletter!

Error: Please check your email address.

More about etworkRSA

Show Comments

Featured Whitepapers

Editor's Recommendations

Solution Centres

Stories by Lucian Constantin

Latest Videos

  • 150x50

    CSO Webinar: Will your data protection strategy be enough when disaster strikes?

    Speakers: - Paul O’Connor, Engagement leader - Performance Audit Group, Victorian Auditor-General’s Office (VAGO) - Nigel Phair, Managing Director, Centre for Internet Safety - Joshua Stenhouse, Technical Evangelist, Zerto - Anthony Caruana, CSO MC & Moderator

    Play Video

  • 150x50

    CSO Webinar: The Human Factor - Your people are your biggest security weakness

    ​Speakers: David Lacey, Researcher and former CISO Royal Mail David Turner - Global Risk Management Expert Mark Guntrip - Group Manager, Email Protection, Proofpoint

    Play Video

  • 150x50

    CSO Webinar: Current ransomware defences are failing – but machine learning can drive a more proactive solution

    Speakers • Ty Miller, Director, Threat Intelligence • Mark Gregory, Leader, Network Engineering Research Group, RMIT • Jeff Lanza, Retired FBI Agent (USA) • Andy Solterbeck, VP Asia Pacific, Cylance • David Braue, CSO MC/Moderator What to expect: ​Hear from industry experts on the local and global ransomware threat landscape. Explore a new approach to dealing with ransomware using machine-learning techniques and by thinking about the problem in a fundamentally different way. Apply techniques for gathering insight into ransomware behaviour and find out what elements must go into a truly effective ransomware defence. Get a first-hand look at how ransomware actually works in practice, and how machine-learning techniques can pick up on its activities long before your employees do.

    Play Video

  • 150x50

    CSO Webinar: Get real about metadata to avoid a false sense of security

    Speakers: • Anthony Caruana – CSO MC and moderator • Ian Farquhar, Worldwide Virtual Security Team Lead, Gigamon • John Lindsay, Former CTO, iiNet • Skeeve Stevens, Futurist, Future Sumo • David Vaile - Vice chair of APF, Co-Convenor of the Cyberspace Law And Policy Community, UNSW Law Faculty This webinar covers: - A 101 on metadata - what it is and how to use it - Insight into a typical attack, what happens and what we would find when looking into the metadata - How to collect metadata, use this to detect attacks and get greater insight into how you can use this to protect your organisation - Learn how much raw data and metadata to retain and how long for - Get a reality check on how you're using your metadata and if this is enough to secure your organisation

    Play Video

  • 150x50

    CSO Webinar: How banking trojans work and how you can stop them

    CSO Webinar: How banking trojans work and how you can stop them Featuring: • John Baird, Director of Global Technology Production, Deutsche Bank • Samantha Macleod, GM Cyber Security, ME Bank • Sherrod DeGrippo, Director of Emerging Threats, Proofpoint (USA)

    Play Video

More videos

Blog Posts

Market Place