Fileless Malware Attacks Continue to Gain Steam

New research shows that attackers are increasingly beating security detection at the gateway and on the endpoint by initiating attacks that don't drop malicious files at all, thus evading file-based detection. And even when they do use malicious files, once they get past the gateway filtering, the typical detection mechanisms aren't picking them up. 

The most recent study comes by way of SentinelOne, which published its Enterprise Risk Index today. This report examines attacks that made it past the gateway and onto endpoints. One of the most damning statistics from the study is the fact that once file-based malware has been filtered by the gateway, it's largely undetectable by AV. 

"One of the more interesting findings from this study is how few pieces of malware actually have signatures within AV engines. Our research team found that only half of file-based attacks had been submitted to malware repositories and, of those, only 20 percent made it to AV engines," says Jeremiah Grossman, chief of security strategy at SentinelOne. "This is yet another data point illustrating how incredibly quickly malware evolves and the impossibility for any signature-based AV solution to keep up."

It's startling considering how many of today's enterprise compromises start at the endpoint and traditional endpoint protections can't even keep up with the file-based malware attacks we've seen for years now. And now the landscape is getting even more complicated, as file-less malware attacks start to rise in prominence. File-less malware attacks evade detection by avoiding the drop of malicious files in favor of methods such as storing information in system memory, leveraging PowerShell or Windows registry, or using malicious macros.

According to SentinelOne's risk index, nearly two in 10 attacks that reach the endpoint start as in-memory attacks that are virtually undetectable to AV systems, no matter how quickly they update signatures.

"In-memory attacks don’t leave detectable artifacts on the file system, and as such, modern anti-malware solutions must watch what processes are actually running, not just what is saved on the system," explains Grossman. "If enterprises don’t have solid protections in place to address in-memory attacks, they’ll get infected; it’s just that simple."

The four months' worth of data from last fall that was compiled for this report, the percentage of endpoint attacks instantiated as in-memory attacks doubled. Last month, Carbon Black released a study among security researchers that showed that close to two-thirds of them have seen an increase in non-malware attacks since the beginning of 2016. This figure includes not only in-memory attacks, but also PowerShell-based attacks, remote logins, WMI-based attacks, and macro attacks. 

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Many organizations only look to identify threats at a single point in time – when a file is written to disk. Malicious files are only part of the problem.

"Cybercriminals are increasingly leveraging non-malware attacks because they provide the path of least resistance and are designed to evade traditional prevention approaches," says Mike Viscuso, co-founder and CTO of Carbon Black. "Once an attack has gained foothold on an enterprise, an attacker will move laterally leveraging existing tools on the operating system. For organizations not prepared to sniff out this kind of behavior, the attack will remain virtually invisible and cause a number of problems.” 

Viscuso says that practitioners need to have non-malware attacks on their radar because at this point, more than half of successful breaches come at the hands of these types of attacks. Anecdotal evidence continues to mount to support the worries of researchers like Grossman and Vicuso. For example, today security start-up Morphisec published details about a politically-motivated attack campaign against Israeli organizations that leans heavily on file-less attack techniques.

In this example, attackers compromised email accounts for high-profile individuals at Ben-Gurion University and sent malformed Word documents in reply to legitimate emails that were designed to take advantage of a Word vulnerability that was patched earlier this month. The documents weaponized with malicious macros installed a fileless variant of the Helminth Trojan agent.

"With many organizations taking high-risk vulnerabilities seriously and patching them as fast as possible, attackers can no longer exploit them," writes Michael Gorelik, vice president of research and development for Morphisec. "We therefore expect that the pendulum will swing back from vulnerability exploits to marco-based campaigns."

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