Attackers are actively compromising Windows systems using an exploit for a previously unknown vulnerability in Adobe's Flash software, according to an analysis of attack traffic by a researcher known as Kafeine.
The attack, confirmed by security firms Symantec and Malwarebytes, is part of a suite of exploits included in the Angler exploit kit, software sold by malware developers to cyber-criminals. The software first attempts to use two older exploits to infect systems through known vulnerabilities in Adobe's Flash Player, and if those fail, uses the new attack, Kafeine wrote in a terse analysis of the attack.
"Disabling Flash player for some days might be a good idea," the reseacher stated.
The attack appears to work on the latest version of Flash running on Microsoft Windows 8.1, the researcher stated in an update on Jan. 22. Microsoft's Internet Explorer and Mozilla's Firefox Web browsers both appear to be affected, while Google's Chrome does not.
Because it affects even the most recent version of Windows, the vulnerability should be considered a high priority to fix, Jerome Segura, senior security researcher at Malwarebytes Labs, stated in an email interview.
"The attack surface is huge, which means that the infection rates per exposure are going to be really high compared to vulnerabilities that have already been patched," he said.
Exploit kits are common attack tools used by less technical criminals to compromise and install malicious software on victim's systems. The kits typically collect a number of exploitation techniques for ubiquitous software, such as Java, Microsoft Office and, increasingly, Adobe Flash. In the past, vulnerability researchers and malware authors targeted Adobe Flash and its estimated 1 billion installations, but for the past few years, vulnerabilities in Java have garnered the most attention. That appears to be changing, Kafeine noted.
Systems compromised by this particular campaign will be infected with click-fraud software and a downloader. Click-fraud software uses the compromised systems to issue impressions—"clicks"—to advertising networks, which results in the criminals getting paid an affiliate fee through the advertising network.
"Unfortunately it is very hard to tell apart real users from fake ones and advertisers essentially end up paying for 'impressions' or 'clicks' where a human being was never involved," Malwarebytes stated in a blog post on the issue.
While click-fraud may not directly impact the owner of the infected system, the attack also installs a downloader, which allows the attacker to install additional — and likely, more malicious — software at a later date.
Anyone using an older version of Windows should consider removing Flash from their system until a patch is provided.
"The danger of any zero-day is that there is no patch in existence, so I would recommend caution from web users until a confirmation and update is issued," Pedro Bustamante, director of Special Projects at Malwarebytes, said in a statement sent to eWEEK. "We would also urge people to update security software."
Researcher Kafeine confirmed that the attack worked on Windows XP, Windows 7 and Windows 8 running Internet Explorer, up to version 10, and Firefox version 35.
Adobe acknowledged the report, but could not immediately confirm the issue. "We are aware of the report and are investigating," a spokesperson stated.