Fileless Malware Takes 2016 By Storm

Malware creators have spent a lot of energy over the years obfuscating the malicious files they drop on infected systems to stay one step ahead of detection mechanisms. This year they're taking their efforts to a new level by dispensing with dropped files altogether. According to security researchers, 2016 saw a surge in attack patterns that had the bad guys taking a fileless approach by executing attacks in memory.

Fileless malware is not a revolutionary approach, but 2016 certainly saw a dramatic rise in this type of attack as the criminals worked to perfect it. A report out earlier this month from Carbon Black says that researchers have found that in the last quarter of 2016, there was a 33% rise in severe non-malware attacks compared to first quarter. The firm reported that over a 90-day period, about one-third of organizations are likely to encounter at least one severe fileless attack.

There are a number of ways that the bad guys are able to carry out these attacks, but those most en vogue as we close out the year are ones that take advantage of PowerShell and Windows Management Instrumentation (WMI) to carry out their dirty deeds - both by carrying out one-time attacks and by loading additional malware once a foothold has been established. Carbon Black researchers note that PowerShell and WMI non-malware attacks shot up by 90% in second quarter of 2016 and are at their highest levels as we speak. In fact, they note that reports show that the Democratic National Committee (DNC) hack earlier this year used a fileless attack that leveraged both PowerShell and WMI in order to get a foot into the door of the political party's systems.

High-profile anecdotal stories like this are adding up and security researchers across the board are bringing to light an increasing number of cybercriminal campaigns taking advantage of fileless attacks. Most recent was a report from Proofpoint earlier this month which examined a November attack campaign involving the August malware variant. Proofpoint researchers say attackers were able to use Office documents weaponized with malicious macros that trigger PowerShell to ultimately load August onto the machine as a byte array.

"The malware itself is obfuscated while the macro used in these distribution campaigns employs a number of evasion techniques and a fileless approach to load the malware via PowerShell," Proofpoint's researchers wrote. "All of these factors increase the difficulty of detection, both at the gateway and the endpoint." 

Heading into 2017, most security researchers don't expect this trend to slow down. According to those with Symantec, the industry should get ready for criminals to make the most of these attacks in the coming year. 

"Fileless infections are difficult to detect and often elude intrusion prevention and antivirus programs," says Brian Kenyon, chief strategy officer for Symantec. "This type of attack increased throughout 2016 and will continue to gain prominence in 2017, most likely through PowerShell attacks. "

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