Yahoo malvertising attack linked to larger malware scheme

Cisco found hundreds of related suspicious domains that are probably used to push malware

A deeper look by Cisco Systems into the cyberattack that infected Yahoo users with malware appears to show a link between the attack and a suspicious affiliate traffic-pushing scheme with roots in Ukraine.

Yahoo said on Sunday that European users were served malicious advertisements, or "malvertisements," between Dec. 31 and last Saturday. If clicked, the advertisements directed users to websites that tried to install malicious software.

Cisco discovered that the malicious websites victims landed on are linked to hundreds of others that have been used in ongoing cyberattacks, said Jaeson Schultz, a threat research engineer.

Schultz looked at domains hosted within a large IP block that researchers observed Yahoo victims were redirected to, finding 393 others that matched a pattern.

The malicious domains all start with a series of numbers, contain between two and six cryptic subdomain labels and end with two random words in the second-level domain, according to Schultz's writeup on Cisco's blog. Some of the domains were still active as of Thursday.

The domains appear to be part of a scheme designed to direct people to malware, Schultz said. The group behind the scam appears to infect legitimate websites with code that redirects people to those malicious domains.

Most of the malicious domains redirect to two other domains that process data for an affiliate program called People who sign up for the program are paid fees to push traffic to other websites.

It wasn't clear whether that program is directly linked to the Yahoo attack, but's site gives the impression that "anything goes," Schultz said.

Further research into the affiliate program's traffic traced it back to other domains used for suspicious purposes, going back to Nov. 28. Some domains are hosted in Ukraine and others in Canada.

Someone involved in the scheme struck gold by somehow inserting malvertisements into Yahoo's advertising network.

"If you can get into the ad networks, especially, that's very lucrative," Schultz said in a phone interview Friday.

The high traffic to Yahoo's site means more people saw the malicious advertisements, which meant a higher rate of infection. Online advertising networks screen advertisements to ensure they're not malicious, but occasionally bad ones sneak in.

The malicious advertisements redirected people to domains hosting the "Magnitude" exploit kit, which tests to see if a computer has software vulnerabilities in the Java application framework.

If Magnitude found a vulnerability, it installed malware such as ZeuS, Andromeda, Dorkbot and ad-clicking malware, according to the Dutch IT firm Fox-IT, which first wrote about Yahoo's problems.

Send news tips and comments to Follow me on Twitter: @jeremy_kirk

Join the CSO newsletter!

Error: Please check your email address.

Tags advertisingCisco SystemsYahoosecurityExploits / vulnerabilitiesinternetmalware

More about CiscoCiscoYahoo

Show Comments

Featured Whitepapers

Editor's Recommendations

Solution Centres

Stories by Jeremy Kirk

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