Only Half of Malware Caught by Signature AV

For years, signature-based antivirus has caught about two-thirds of threats at the network edge — in the last quarter, that success rate has plummeted to only 50%, according to WatchGuard Technologies' latest quarterly report, published on December 11.

The network security firm found that the percentage of malware that successfully bypassed signature-based antivirus scanners at companies' network gateways has increased significantly, either by scrambling code — known as "packing" — using basic encryption techniques or by the automatic creation of code variants. In the past quarter, the share of malware using these obfuscation techniques has jumped to 50% of malicious programs detected at the edge of the network, bypassing common antivirus engines, the company found.

Dubbed "zero-day malware," these attacks demonstrate how attackers have adapted to the decades-old signature-based antivirus scanning technology, says Corey Nachreiner, chief technology officer at WatchGuard Technologies.

"The big change is that more and more malware is becoming evasive, so that signature-based protection is no longer sufficient," he says. "There is nothing wrong with having it, because it will catch 50% to two-thirds of the traffic, but you definitely need something more." 

In the first quarter of 2019, the company saw signature antivirus catch 64% of malware. In the second quarter, that dropped only slightly to 62%. In 2017, antivirus firm Malwarebytes found that using two signature-based antivirus engines still only caught about 60% of threats.

While the statistic applies only to the BitDefender antivirus engine used in WatchGuard's product, Nachreiner argues that the scanner is better than average — based on VirusTotal detections — suggesting that malware is even more successful getting past other companies' products.

"The reason that we feel that we can extrapolate from a single engine is that we use VirusTotal all the time, and BitDefender is always one of the first to detect threats," he says. "We feel that extrapolation, while not exact, will be very representative, even conservatively, of the capabilities of signature-based engines."

Zero-day malware — not to be confused with zero-day exploits — need to be caught by technologies other than signature-based antivirus, he says. WatchGuard, for example, incorporate three different anti-malware services into its product, including machine learning-based pattern detection and a sandbox service to catch threats based on their execution behavior.

The rise in evasive malware is the most significant trend in WatchGuard's "Internet Threat Report: Q3 2019," but the company also saw a general rise in network attacks — those attempts that attempt to actually compromise a network — of about 8% from the previous quarter.

Attacks using SQL injection, cross-site scripting, and brute-force credential stuffing topped the list of attacks the company detected in the third quarter of 2019, but the top 10 network-based attacks also include exploits aimed at two older vulnerabilities in the Apache Struts web application framework, security issues that led to the massive breach of data-collection firm Equifax. The company missed patching key servers that were then compromised by attackers, leading to the leak of information on about 148 million Americans. The breach led to a $700 million fine and, because of his stock trading prior to public notification of the breach, the conviction of the former CIO on insider trading.

"With a 10 of 10 for severity in the National Vulnerability Database and the national attention the Equifax breach got from this vulnerability, we hope web admins have already upgraded their servers," WatchGuard stated in the report. "If you've patched, this attack won't work ... [but] vulnerable servers won't last long while connected to the Internet."

The increase in attacks on older vulnerabilities makes it even more important for companies to look to their patching processes and make sure that they are not missing any servers, Nachreiner says.

"After Equifax, you would have hoped that everyone had patched immediately, but the fact that the attackers are ramping up attacks could mean that they have seen some success," he says. "So, you need to ask, have you really patched the Apache Struts vulnerability? Check your environment to make sure that you are not vulnerable."

The WatchGuard report gathers data from users that have opted into its data-collection program, about 37,000 devices in the latest quarterly report. 

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