TAILIEUCHUNG - Microsoft Encyclopedia Of Security Phần 9

Tổng quan Transmission Control Protocol (TCP) sử dụng một quá trình bắt tay ba chiều để thiết lập kết nối giữa hai máy. | SYN scan Syskey SYN scan A type of stealth scan that makes use of SYN packets. Overview Transmission Control Protocol TCP uses a three-way handshake process to establish a connection between two hosts for which the following steps take place 1- The host wishing to establish the connection sends a SYN packet to the target host to request a socket connection. 2- The target host responds with a SYN ACK that acknowledges receipt of the original SYN packet and sends its own SYN to request a socket. 3- The originating host replies with an ACK and a connection between the two hosts is established. In a SYN scan an attacker sends a SYN packet to a port on a target host to see how the host responds. If the host responds with a SYN ACK packet this means the targeted port is listening open and may be targeted for further attack. Meanwhile the attacker simply drops the received SYN ACK packet instead of acknowledging it which means a connection is not established with the target host. Alternatively the attacker might respond with an RST packet which can sometimes help prevent the remote host from logging the connection attempt. If the target port on the remote host is not listening the remote host responds with an RST packet instead or possibly provides no response if a firewall blocks RST packets from leaving the network . Notes Because a SYN scan fails to complete a TCP connection that the attacker tries to initiate with the target it is sometimes called a half-open scan. 1 Attacker SYN to 3 Drop packet Web server target SYN scan. How a SYN scan works. See Also port scanning stealth scanning Syskey A Microsoft Windows NT utility for strengthening password security. Overview Syskey first was released as a post-Service Pack 2 SP2 hotfix for Windows NT and later was included as part of Service Pack 3. Syskey helps protect Windows NT passwords by implementing strong 128-bit encryption for password hashes instead of the previous 40-bit level of encryption. Should an attacker .

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