This is why its a good idea to always have a proper anti-virus program running... Although most anti-virus software do not protect the computer from spyware or adware. Hackers use these programs to gather information from your computer as well as making changes to internal settings creating more vulnerabilities for other threats.
The best solution for these types of problems is to always update your operating system, have a spyware and anti-virus software installed and scan your computer periodically.