Those findings come via Microsoft Safety Scanner (MSS), a free, recently updated tool from Microsoft that's designed to clean up after a malware infection. The tool expires 10 days after being downloaded to force users to download a new version with the latest updates.
After recently updating MSS to scan 64-bit Windows systems, Microsoft compiled seven days' worth of scans, and found that "seven of the top 10 threats are files containing exploits for Java vulnerabilities," according to a blog post from Scott Wu and Joe Faulhaber at the Microsoft Malware Protection Center.
The most-seen malware was OpenCandy adware, present on 0.8% of all PCs scanned. But almost every other piece of prevalent malware contained code for exploiting Java vulnerabilities, including a Java Runtime Environment (JRE) bug discovered in 2008.
To illustrate the types of malware its scanner found on PCs, Microsoft detailed the malware found just on the 0.5% of PCs exploited via the 2008 JRE bug: Alureon rootkit (on 7.3% of those PCs), browser modifier Zwangi (6.0%), rogue application Winwebsec (5.7%), and Hotbar and ClickPotato adware (both 5.4%).
"Of course many of these detections by MSS are the debris or aftermath after the exploit has already executed," said Wu and Faulhaber. "By the time a user downloads and runs MSS to detect malware, the machine may have already been infected, if it was vulnerable to the exploit at the time." That's why Microsoft says MSS is "not a replacement for using an antivirus software program that provides ongoing protection" and which could have prevented an infection in the first place.
In 2011, the Java threat doesn't appear to have diminished. According to a study by Kaspersky Labs that looked at malware trends from January through March 2011, Java vulnerabilities comprised a significant portion of the top 10 "most seen" vulnerabilities on people's PCs. "Vulnerabilities in Adobe products occupied five positions in the list, including 1st and 2nd places, while 4th and 5th positions were taken up by vulnerabilities in the Java Virtual Machine," said Yury Namestnikov, a security researcher at Kaspersky, in a blog post. The remaining top 10 vulnerabilities involved Apple QuickTime, Winamp, and Microsoft Office.
"All of the vulnerabilities that appeared in the Top 10 enable cybercriminals to take control of computers at the system level," said Namestnikov.
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