Very aggressive weaponized Word documents have been getting past standard defenses in May, according to a new report from security firm Invincea.
Invincea offers a security technology that isolates the four most common infection vectors -- the browser, email clients, Office applications, and PDF readers -- into an isolated container. This allows the company to detect previously unknown strains of malware as it tries to escape from these containers.
"We are the last chance for defense for a lot of hosts and end points," said Patrick Belcher, Invincea's director of malware analysis.
For example, the Dridex malware campaign used fast-changing, malicious Word documents. These particular attachments would execute malicious scripts whenever the document was opened -- even if the scripting was disabled.
"Even if you don't have Visual Basic scripting enabled, or don't allow macros to run on document open, these particular things bypass that," Belcher said. "You just have to open the document."
The Dyreza phishing campaign also used rapidly-evolving weaponized Word documents to create backdoor access points to user computers and then steal banking and password information.
Weaponized Word documents were also key to the Nitlove Point of Sale malware, which also installs click-fraud botnets and the Pony information stealer and banking Trojan.
Invincea also reported on the Rombertick malware, which threatened to destroy hard drives if tampered with. However, what Rombertick actually did instead is collect a mass of information about a computer's user -- the kind of information that's of higher potential interest to advertisers than to cyber criminals.
According to Invincea, this is an example of spyware copying evasion techniques from the malware universe.
One more type of malware got through traditional defenses last month, malvertising that used Flash overflows to assemble malware using the native scripting features built into Windows.
"They're able to download additional pieces of malware, or script it out using the old 'echo' command, writing code right from the malware," said Belcher.
He added that Invincea has seen this approach working against fully-patched versions of Internet Explorer as well as against fully-patched versions of Flash.
"The surprising stuff is how prevalent it is," he said. "People talk about malvertising, about making it better, but it doesn't seem to be the case from my point of view. It seems to be getting worse, not better."
The Doubleclick advertising network was the hardest hit, Belcher said.
"But they are no worse than any of the other ones," he added. "They partner with so many other advertising networks on the the back end. It takes just one of the back-end partners to switch out one of the ads with malicious advertising."