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 i...