Computer security is essential to protect against threats caused to the computer system that occur due to its vulnerability. The threat to IT security comes from a person, event or circumstance, which may be intentional for financial reasons or unintentionally by deleting some important data. A threatening agent depends on method, opportunity, and motivation. The method is knowledge to attack, an opportunity to access necessary information, and a motive behind the attack. Previously, in the 1980s and 1990s, this was done for personal glory, but in the 2000s, it was done for financial purposes to make profits. Cybercriminals are merging with established crime and espionage forces to obtain financial rewards. Internet misuse has also increased significantly. Cyberterrorism is one of the main problems related to the hacking of a country's sensitive data and military plans. These attacks are also called cyber information warfare and it is very difficult to trace the original identity or source to the point of attack. computer security protects the computer in three ways in case of lack of availability, integrity and confidentiality or confidentiality. Lack of availability is a denial of service that poses a serious threat to life and society as more and more people now depend on computers. Integrity is making programs exactly as they are. Any modifications to the programs must be made only by an authorized person to maintain the accuracy, quality and precision of the data. The third is confidentiality, which constitutes inappropriate disclosure of data. A security policy is one that defines what actions to allow, access to resources and what to protect against which threats in order to achieve the ......middle of paper ......section systems monitor in order to warn of an attack that could be imminent, in progress or has already occurred. Intrusion prevention systems work like the detection systems that identify attacks in progress and also predict and stop the intrusion that is about to occur. Finally, when the attack has occurred, the affected system will study the attack to know what happened, how to prevent its occurrence, and its level. damage. Forensic experts study the attack and act much like any other investigative system by comparing the appearance of important pieces of evidence and suggest connections between pieces of evidence using their experience. Computer Emergency Response Teams are also another organization that takes care of computer security by collecting data on vulnerabilities and attack patterns and warning them of danger and possible countermeasures..