Adding the fast-spreading Java zero-day exploit to BlackHole has more than doubled the crimeware toolkit's potency, according to researchers who are tracking the threat.
After exploit details for two Java 7 vulnerabilities were leaked and began turning up over the weekend, BlackHole's authors worked quickly to update their commercially available application to include the attack code. And this prompt action appears to have paid off for the fraudsters.
BlackHole works by distributing exploits to computers that visit compromised websites.
"Usually, a good exploit kit like BlackHole has a success rate of around 10 percent for infecting machines visiting [its malicious] servers," security firm Seculert wrote in an blog post. "In the new version of BlackHole infection servers, we have seen up to a 25 percent success rate."
The company estimates that tens of thousands of computers are newly infected with malware. Most of the infections have been delivered through Internet Explorer and Firefox, and affected systems in Russia and surrounding countries. However, a large number of machines in the United States also have been hit.
Experts recommend users to disable Java in the browser until Oracle, which maintains the software platform, releases a patch. Even Mozilla has suggested that its Firefox users disable the Java plug-in in advance of a fix.
Oracle has not said whether that will be before the company next is scheduled to patch Java, on Oct. 16. A report on Wednesday suggested the database giant may have known about the bugs since last spring.