A rise in malware has caused the number of infected PCs worldwide to increase 15 percent just from August to September, says a report released Tuesday from antivirus vendor Panda Security.

Across the globe, the average number of PCs hit by malware now stands around 59 percent, an all-time high for the year. Among 29 countries tracked, the U.S. ranked ninth with slightly more than 58 percent of its PCs infected. Taiwan hit first place with an infection ratio of 69 percent, while Norway came in lowest with only 39 percent of its PCs attacked by malware.

(Credit: Panda Security)

The study found that in the U.S., Trojans and Adware were the two most pernicious types of malware, followed by worms and viruses.

(Credit: Panda Security)

"This is a clear sign that hackers are becoming more and more sophisticated," said PandaLabs Technical Director Luis Corrons. "Cybercriminals have found news ways to spread their creations, frequently exploiting the latest news stories to launch attacks through social networks, videos, and e-mail. The huge amount of Trojans in circulation is due to the spectacular increase in the number of banker Trojans aimed at stealing user data."

The company based its results on data taken from users who scanned their PCs with the free Panda ActiveScan online tool. The results for September were gathered from August 28 to September 28 and compared with the results from July 28 to August 27.