Without antispyware your computer will be infected with spyware and adware. Spyware attempts to collect personal information without your knowledge. Spyware might be installed as part of a worm or a Trojan horse. It has the ability to transmit personal information to whoever installed it on your computer. Adware are small pieces of software which track your Internet surfing habits. It uses this information to send you advertisements based on what it thinks your interests are. Besides the dangers that adware and spyware cause, these programs are also poorly written. The poor writing often causes them to use excessive computer resources or lead to system crashes.