Malware (malicious software) is software intended to infiltrate and damage or disable computers. Malicious software attacks have existed for decades and according to the 2014 Information Security Breaches Survey, commissioned by the Department for Business, Innovation and Skills, more than 25% of UK SMEs suffered a virus or other malicious software attack in 2013.
There are two main types of malware. Software viruses are executable files loaded onto your computer either without your knowledge or when run you remain unaware of their effects. Macro viruses use the macro facilities found in many types of software to achieve the same effect.
To cause damage, malware must get onto one of your computers and then be executed. Like a physical virus, just because you suffer no ill effects it doesn’t mean you don’t have an infection. And, you can infect and damage others by unknowingly passing on the malware.