Macro-based malware is making a comeback, researchers warn

Attackers bypass defenses aganst macros with social engineering to install malware

For the past several months, different groups of attackers have distributed malware through Microsoft Office documents that contain malicious macros, reviving a technique that has been out of style for over a decade.

Macros are scripts that contain commands for automating tasks in various applications. Microsoft Office programs like Word and Excel support macros written in Visual Basic for Applications (VBA) and these can be used for malicious activities like installing malware.

To prevent abuse, starting with Office XP, released in 2001, users are asked for permission before executing unsigned macros embedded in files, this being the primary reason why attackers have stopped using macros in favor of other malware distribution methods.

However, it seems that when coupled with social engineering the technique can still be effective and some cybercriminal groups have recently started to exploit that.

"The Microsoft Malware Protection Center (MMPC) has recently seen an increasing number of threats using macros to spread their malicious code," malware researchers from Microsoft said in a blog post last Friday.

Two such threats that primarily target users in the U.S. and U.K. and whose activity peaked in mid-December are called Adnel and Tarbir. Both are distributed through macros embedded in .doc and .xls documents that are delivered via spam emails and typically masquerade as receipts, invoices, wire transfer confirmations, bills and shipping notices.

When opened, the documents provide victims with step-by-step instructions on how to enable the untrusted macros to run, the Microsoft researchers said. "The combination of the instructional document, spam email with supposed monetary content, and a seemingly relevant file name, can be enough to convince an unsuspecting user to click the Enable Content button."

Another malware program that's being distributed through macros is called Dridex and targets online banking users. At their peak in November, the Dridex-related spam campaigns distributed up to 15,000 documents with malicious macros per day, according to researchers from security firm Trustwave.

The documents posed as invoices from software companies, online retailers, banking institutions and shipping companies and some of them had instructions on how to enable the macros to run, the Trustwave researchers said Tuesday via email.

It's not just cybercriminals who began using the macros technique again, but also state-sponsored attackers. Researchers Gadi Evron and Tillmann Werner recently presented their analysis of a cyberespionage operation dubbed Rocket Kitten at the Chaos Communication Congress in Hamburg. The attackers targeted government and academic organizations in Israel and Western Europe using spear-phishing emails that contained Excel files with malicious macros. When run, the macros installed a sophisticated backdoor.

Another cyberespionage campaign that used Word documents with malicious macros was CosmicDuke, which was uncovered in September and targeted at least one European Ministry of Foreign Affairs. "It's heartwarming to see how kind the attackers are: when you open the email attachment, the Word document helps you enable macros by instructing you to click 'Enable Content'," researchers from F-Secure said Wednesday in a blog post discussing connections between the CosmicDuke, MiniDuke and OnionDuke malware programs.

Join the CSO newsletter!

Error: Please check your email address.

Tags trustwaveMicrosoftsecuritymalware

More about ExcelF-SecureMicrosoftTrustwave

Show Comments

Featured Whitepapers

Editor's Recommendations

Solution Centres

Stories by Lucian Constantin

Latest Videos

  • 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

  • 150x50

    IDG Live Webinar:The right collaboration strategy will help your business take flight

    Speakers - Mike Harris, Engineering Services Manager, Jetstar - Christopher Johnson, IT Director APAC, 20th Century Fox - Brent Maxwell, Director of Information Systems, THE ICONIC - IDG MC/Moderator Anthony Caruana

    Play Video

More videos

Blog Posts