An attack is any malicious or accidental disruption of the confidentiality, integrity, or availability of information and network resources. Attacks can come from many places, electronic, physical or human. Electronic attacks can come from the external network (Internet) or from the internal network (Intranet); physical attacks can come in the form of sabotage or theft of hardware and equipment, while human attacks most often come in the form of social engineering. Some of the attacks identified and evaluated in this paper are: spoofing, replay attacks, access suppression-relay attack, and origination and repudiation attack. Spoofing occurs when attackers try to appear to be someone else, usually a genuine user. The phenomenon of Web spoofing, or the creation of misleading Web sites that faithfully represent real sites in order to extract personal financial data from unwary Web visitors, is a common form of online scam that helps identify credit and financial fraud based on and threat of undermine consumer confidence in the Internet. purchases and banking operations. The FBI defines spoofing as "the hottest and most troubling new scam on the Internet contributing to the increase in identity theft, credit card fraud, and other Internet fraud." Approximately thirty such hoax attack sites are detected every day, although many more go undetected. Replay attacks occur when the attacker attempts to capture packets on their way from one host to another and then replay them on a targeted host in an attempt to imitate a legitimate user or system. The replay attack is easy because it is not difficult to capture the commands to replay. A user on a network can run a sniffer program and capture all packets traveling over the network. The Replay attack seeks systems with weak... half of card ......and the disadvantages of both symmetric and asymmetric encryption are: Symmetric Advantages • Use password verification to prove the identity of the recipient • Encrypted data can be transferred over the link even if there is a possibility that the information will be intercepted. No key is transmitted with the information, the likelihood of the data being decrypted is unlikely • Secure • Fast and easy to implement Symmetric Disadvantages • Cannot provide digital signatures that cannot be repudiated • share keys • cause a lot of damage if compromised • have difficulty with key transportAsymmetric advantages• Scalable and does not require much administration• Easy for the user to use• Can provide digital signatures that can be repudiatedSymmetric disadvantages• slower due to longer key length• complexity of the encryption algorithm used