For the last two weeks, based on reports to and observations made by Symantec, an established family of malware has been launching print jobs that do nothing but waste paper.
The source of the attacks is unknown. However, the areas with the most cases of attack are concentrated in the U.S. and India, followed by the EU and South America, but those areas are only somewhat impacted.
Symantec calls the printer malware Milicenso, and code examination marks it as a variant of a malware delivery system discovered in 2010. Think of it as a malware system for hire, Symantec explained, noting that the payload most commonly associated with this Milicenso is Adware.Eorezo; an adware targeting French speaking users.
It compromises the victim’s system through malicious email attachments or Web-based scripts. In their report on the malware, Symantec said that they’ve seen a large number of samples that appear to be codecs.
The malware keeps itself encrypted to hinder analysis, and it goes through some internal system checks in order to ensure that the malware isn’t running on a VM or analysis engine such as Threat Expert.
“However, in this case despite detecting the presence of a sandbox the threat, instead of ceasing all activity, actually performs certain specific activities, such as contacting sites,” Symantec’s write-up on the malware explains.
“These actions are associated with Adware.Eorezo and it seems that it is using the adware as a decoy to distract attention from itself, thereby attempting to avoid malware analysis as this would categorize it as low risk and be dismissed.”
As it turns out however, the Adware is buggy. During the infection phase, a .spl file is created in an alternate print spool folder created by the malware. “The .spl file, while appearing to be a common printer spool file, is actually an executable file and is detected as Adware.Eorezo. Depending on the configuration, any files, including binary files, created in that folder will trigger print jobs,” Symantec explained.
“This explains the reports of unwanted printouts observed in some compromised environments. Based on what we have discovered so far, the garbled printouts appear to be a side effect of the infection vector rather an intentional goal of the author.”
More details are available here.