What are the common computer threats? What's the harm?

Q: What are the common computer threats and what are the hazards?

Trojan Horse is the most common computer threat, is the intrusion of user computers, opportunistic steal account password malicious program. Usually, the Trojan will automatically run, in the user login game account or other (such as net silver, chat) account, record the user entered the account password and sent to the designated mailbox, thereby stealing user account password, transfer account of the virtual property, to you caused loss. It is recommended that you can use professional anti-Trojan tools (such as: Baidu Guardian) to protect against Trojans.