TechCrunch reports that the Purple Fox malware, which was first discovered in 2018, is increasingly growing in size due to a new infection method that spreads the malware from one machine to another. The malware targets the server message block to guess weak user account passwords from internet-facing Windows computers, said Guardicore researchers Amit Serper and Ophir Harpaz, who revealed the new technique. Once it has accessed the computer, the malware then delivers a malicious payload and installs a rootkit that makes it harder to be removed or detected. "The fact that it’s an opportunistic attack that constantly scans the internet and looks for more vulnerable machines means that the attackers can sort of 'set it and forget it'," said Serper, Guardicore’s vice president of security research for North America. According to Guardicore data, Purple Fox infections have risen by 600% since May of last year, and the actual number could amount to more than 90,000 infections in the previous year.