Symptoms of Malware Regardless of the type of malware a system has been infected with, these are common malware symptoms: There is an increase in CPU usage. There is a decrease in computer speed. The computer freezes or crashes often. There is a decrease in Web browsing speed. There are unexplainable problems with network connections. Files are modified. Files are deleted. There is a presence of unknown files, programs, or desktop icons. There are unknown processes running. Programs are turning off or reconfiguring themselves. Email is being sent without the user’s knowledge or consent.