Use anti-virus software
German security institute AV-Test found that in 2010 there were 49m new strains of malware, meaning that anti-virus software manufacturers are engaged in constant game of "whack-a-mole". Sometimes their reaction times are slow – US security firm Imperva tested 40 anti-virus packages and found that the initial detection rate of a new virus was only 5%. Much like flu viruses and vaccine design, it takes the software designers a while to catch up with the hackers. Last year AV-Test published the results of a 22-month study of 27 different anti-virus suites and top-scoring packages were Bitdefender, Kaspersky and F-Secure. Meanwhile, security expert Brian Krebs published the results of a study of 42 packages which showed on average a 25% detection rate of malware – so they are not the entire answer, just a useful part of it.