CAPEC Definitions / CAPEC-287
CAPEC-287: TCP SYN Scan
An adversary uses a SYN scan to determine the status of ports on the remote target. SYN scanning is the most common type of port scanning that is used because of its many advantages and few drawbacks. As a result, novice attackers tend to overly rely on the SYN scan while performing system reconnaissance. As a scanning method, the primary advantages of SYN scanning are its universality and speed.
Extended Description
RFC 793 defines the required behavior of any TCP/IP device in that an incoming connection request begins with a SYN packet, which in turn must be followed by a SYN/ACK packet from the receiving service. For this reason, like TCP Connect scanning, SYN scanning works against any TCP stack. Unlike TCP Connect scanning, it is possible to scan thousands of ports per second using this method. This type of scanning is usually referred to as 'half-open' scanning because it does not complete the three-way handshake. The scanning rate is extremely fast because no time is wasted completing the handshake or tearing down the connection. This technique allows an attacker to scan through stateful firewalls due to the common configuration that TCP SYN segments for a new connection will be allowed for almost any port. TCP SYN scanning can also immediately detect 3 of the 4 important types of port status: open, closed, and filtered.
Mitigations
No Mitigations found.
Relationships with other CAPECs
CAPEC-300: Port Scanning
Prerequisites
This scan type is not possible with some operating systems (Windows XP SP 2). On Linux and Unix systems it requires root privileges to use raw sockets.
Related Weaknesses
CWE-200: Exposure of Sensitive Information to an Unauthorized Actor
