Wi-Fi networks make an excellent breeding ground for worms and other malware, according to a newly published university study. According to a study published this week in the Proceedings of the National Academy of Sciences, four researchers at Indiana University in Bloomington conducted a series of simulated malware attacks on Wi-Fi networks in seven U.S. cities that produced an epidemic spreading to thousands of Wi-Fi routers in less than 24 hours. A simulated attack in New York infected more than 18,000 wireless routers in a two-week time span.

Security researchers have known for some time that Wi-Fi access points are vulnerable to the spread of malware and other exploits. However, the university simulation shows the full effect of a Wi-Fi worm, and proves that the infection does not have to spread to attached PCs to wreak havoc.

Like a parasite living off of its host, an infected router could simply monitor PCs' Internet connections and relay nonencrypted traffic back to the worm's creators, said Steven Myers, assistant professor at Indiana University's School of Informatics, in an interview with IEEE Spectrum. The infected router could then search the data streams for credit card information or other valuable data, he said.

Myers said that since wireless routers generally do not run antivirus software, there might not be a way to clean an infected router. But users can prevent most infection threats by using strong passwords and WPA -- not WEP -- for encryption.