Complex sentence: SpySheriff is malware that disguises itself as an anti-spyware program, to trick the owner of the infected computer to buy the program, by repeatedly informing them of false threats to their system.
Split into simpler sentences: SpySheriff is malware that disguises itself as an anti-spyware program. The program attempts to trick the user of an infected computer into buying the program by repeatedly informing them of false threats to their system.