A new exploit that prompted Adobe to release an emergency patch for Flash Player was used in targeted attacks that distributed malware designed to steal log-in credentials for email and other online services, according to researchers from antivirus firm Kaspersky Lab.
Adobe released new versions of Flash Player for Windows, Mac and Linux Tuesday in order to address a critical remote code execution vulnerability for which, the company said, an exploit existed in the wild. Kaspersky Lab researchers Alexander Polyakov and Anton Ivanov were credited with reporting the vulnerability.
Eleven SWF (Flash) exploit files that targeted this vulnerability were found, but only one of them contained an executable file as a payload, the Kaspersky Lab researchers said Wednesday in a blog post about their findings.
Some of the other exploits were designed to execute a file from URLs passed to them as a parameter, but the researchers couldn't identify the actual URLs that attackers had used or the files they pointed to.
The SWF files came embedded into .docx files -- Microsoft Word documents -- that had Korean names, but were found on computers in China, the researchers said.
In one case one of the rigged documents was sent as an attachment to an email address registered with 163.com, a Chinese email provider, and was opened from an email client on a computer running Mac OS 10.6.8. However, the exploit was clearly designed to target Windows users.
In two other cases the malicious docx files were found on Windows 7 machines in the cache of Internet browsers, particularly a browser of Chinese origin called Sogou Explorer. This doesn't mean the files hadn't been delivered via email, the Kaspersky researchers said.
The only recovered payload consisted of an executable file that acted as a downloader for additional malware files. The Kaspersky researchers were able to recover two such files.
The first one was a Trojan program designed to steal log-in credentials saved in locally installed programs including Foxmail, OperaMail, Opera, Mozilla Firefox, Safari, IncrediMail, Pidgin and Thunderbird, the Kaspersky researchers said. It also steals data entered into Web forms on a variety of websites, many of which are webmail providers. The list of targeted websites includes Twitter, Facebook, Yahoo, Google, Live.com, AOL.com, Yandex, Mail.ru, gmx.com, fastmail.com, 163.com, lycos.com, mail.com, zoho.com and others.
The second file is a backdoor program that works in conjunction with the first malware, the researchers said. It connects to three command-and-control servers and downloads additional DLL files hidden inside JPEG images.
"We are continuing to follow the bot's activity," the Kaspersky researchers said.
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