Assalamualaikum.....i back!!!=) now i want to revision about important topic, and i thing this topic is very usefull for u=)

Title : Computer security and safety, ethisc and privacy

Computer security is a branch of computer technology known as information security as applied to computer and network.Every computer must be a security so that computer can not entered by virus.
Another point is cybercrime. Cybercrime is an online or Internet-based illegal act such as ,

• Hacker
• Cracker
• Script Kiddies
• Corporate Spies
• Unethical Employees
• Cyberextortionists
• Cyberterroirists

An infected computer has one or more of the following symptoms :

• Operating system runs much slower than usual
• Available memory  is less than expected
• Files become corrupted
• Screen displays unusual message or image
• Music or  unusual sound plays randomly
• Existing programs and files disappear
• Program or files do not work properly
• System properties change
• Operating system does not start up
• Operating system shuts down unexpectedly

 A backup is a duplicate of a file , program , or disk that can be used if the original is lost , damaged  or destroyed to back up a file means to make a copy of it.
Have a to type of backup :

• Full backup
• selective backup

Wireless is a refers to any type of computer network that is not connected by cables of any kind. It is a method by which homes, telecommunications netwocrk and enterprise (business) installations avoid the costly process of introducing cables into a building, or as a connection between various equipment locations. Wireless telecommunicatios networks are generally implemented and administered using a transmission system called radio waves. This implementation takes place at the physical level (layer) of the OSI model network structure.