Attackers drop web exploits for macros and trickery

  • Liam Tung (CSO Online)
  • 23 February, 2016 19:03

New research shows that old-fashioned spam and trickery is the most common way of infecting machines, driven largely by Dridex banking malware.

Over the course of 2015 cybercriminals turned away from technically sophisticated software exploits towards cheaper and possibly more effective social engineering that tricks people to infecting their own machines, according to security firm Proofpoint.

“The year 2014 was all about the technically sophisticated attacker. We saw levels of software coding and ingenuity that were very impressive. These were people that spent lots of time and money and the guys in the underground forums were offering bounties of millions of dollars for technical exploits. Over the past year the pendulum went all the way in the other direction. As humans, we’re a lot easier to exploit and cheaper,” Kevin Epstein, VP of threat operations at Proofpoint told CSO Australia.

Analysing a subset of its own customers data, Proofpoint found that in 2015 99.7 percent of documents used in attachment-based campaigns contained malicious macros to compromise a target rather than automated exploits.

Macros in Microsoft’s Word, for example, are disabled by default to reduce the risk of attackers exploiting them to install malware. Epstein said a typical method to convince people to undo that protection is by creating a document with a blurred image and instructions that tell the recipient the image was blurred for their protection and that to view it requires enabling macros.

In instances where attacker email contained a URL, 74 percent led to pages designed to phish credentials while 26 percent sent victims to a page that encouraged them to run a malicious program, for example by downloading a Word document from Dropbox.

According to Epstein, just two percent of the attack email linked to a web page hosting an exploit kit. In other words, very few attacks required no human interaction.

The most common malware last year were banking Trojans, accounting for 74 percent of all payloads. Dridex banking malware, as measured by message volume, was ten times greater than the next most common malware.

Despite efforts by law enforcement to take down Dridex’s infrastructure, the botnet emerged as one of the key sources of malware infections last year.

Symantec recently estimated that Dridex accounted for 48 percent of infections in 2015, peaking at 16,000 infections per day in June, achieved exclusively by massive spam campaigns that only operate between Monday to Friday.

Nearly all Dridex campaigns rely on Word documents laced with a malicious macro that installs malware designed to steals banking credentials via a man-in-the-browser attack. Last week however the same infection method was used to spread the new Locky ransomware, suggesting Dridex was expanding from stealing banking credentials to holding data at ransom through file encryption software.

Epstein said Proofpoint gathered its data over a year from a subset of customers that volunteered to share their data with the company. He declined to say how many customers data was used for the study.

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