Portions of Monster.com went black on Monday after attackers hijacked job listings hosted on the popular employment website and used them to spread malware to visitors, a security researcher said.

The outage affected the Monster Company Boulevard, said Exploit Prevention Labs' Roger Thompson, who first noticed the site was inaccessible around 5 pm Monday East Coast time.

Several hours earlier, he discovered the site had been subject to an iFrame attack that was redirecting visitors to servers that hosted exploits from Neosploit, a nasty attack toolkit that competes with better-known packages such as MPack and Icepack. Thompson detected the attack through data anonymously submitted through LinkScanner, an Exploit Prevention Labs' product that warns web users when they reach dangerous online destinations.

The iFrame attack marred employment listings offered by some of the world's biggest companies, including Best Buy, Toyota Financial and Eddie Bauer, Thompson said. People who visited those listings were redirected to a server that hosted the exploits. The malicious javascript was encrypted, making it hard to know exactly how it behaved.

Monster.com has since scrubbed its pages clean of the offending code and restored the pages it took down, a spokesman said in a statement. The attack attempted to install malware that is commonly flagged by most anti-virus programs and "should not affect users running Windows with the most recent security updates from Microsoft," according to the statement. Only "an extremely small percentage of those using the site this week were potentially exposed prior to those pages being cleaned."

Thompson confirmed he is no longer detecting the malicious iFrames.

This is at least the second time criminals have penetrated Monster.com in an attempt to attack its users. In late August, the company warned that hackers had stolen user names which were being targeted in highly tailored phishing and spam attacks. The acknowledgment came almost a week after Symantec first uncovered the breach.®

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