Hackers usually try to make their malware stick to victims’ PCs, but a group behind recent attacks exploiting an un-patched flaw in Internet Explorer (IE) are using malware that vanishes on reboot, signalling a shift in strategy to frustrate forensic investigators.
This week’s Patch Tuesday will offer an interesting set of updates for Microsoft’s customers, with eight slated for critical flaws in Windows and every version of IE, from IE 6 to IE 11. Microsoft last week acknowledged flaws in Office, Windows and Lync that it won’t be patching, but it hasn’t said whether or not the zero-day flaws it is patching in IE are under attack.
Security firm FireEye last week reported an IE flaw was being used in a “watering hole” attack (a targeted drive by attack) that was hosted on a US-based website. According to the firm, the attack exploited a previously unknown “out-of-bounds memory access vulnerability” affecting different configurations of IE 7, 8, 9 and 10 on Windows XP and Windows 7.
FireEye reported last week that the IE zero-day was hosted on a “compromised website based in the US” and on Sunday elaborated on its research, suggesting it was aimed people who work in the US defence sector.
“The attackers inserted this zero-day exploit into a strategically important website, known to draw visitors that are likely interested in national and international security policy,” FireEye researchers Ned Moran, Sai Omkar Vashisht, Mike Scott and Thoufique Haq wrote on Sunday. The researchers didn't name the website.
However, they noted the hackers behind this attack share the same infrastructure as the hackers behind the breach of security firm Bit9 earlier this year as well as more recent attacks on Japanese targets in September, also using zero-day flaws in IE.
The hackers are also employing novel methods to frustrate forensic investigation techniques used by companies like Mandiant, which earlier this year fingered Chinese hacking crew APT-1 for sustained attacks on US companies.
Whether for spying or stealing credentials, hackers generally prefer their malware to persist on a compromised system, even after the machine is rebooted. But the malware, which FireEye has labelled Trojan.APT.9002, unusually sacrifices persistence.
“The attackers loaded the payload used in this attack directly into memory without first writing to disk – a technique not typically used by advanced persistent threat (APT) actors. This technique will further complicate network defenders’ ability to triage compromised systems, using traditional forensics methods.”
By opting for non-persistent malware, the hackers traded better evasion for a higher risk of losing control over already compromised machines. It also suggests the hackers were confident they could achieve their goal in a relatively short window, according to FireEye’s researchers.
“The fact that the attackers used a non-persistent first stage payload suggests that they are confident in both their resources and skills. As the payload was not persistent, the attackers had to work quickly, in order to gain control of victims and move laterally within affected organisations.
"If the attacker did not immediately seize control of infected endpoints, they risked losing these compromised endpoints, as the endpoints could have been rebooted at any time – thus automatically wiping the in-memory Trojan.APT.9002 malware variant from the infected endpoint.”