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What is a TCP or UDP based port scan?
UDP scans, like TCP scans, send a UDP packet to various ports on the target host and evaluate the response packets to determine the availability of the service on the host. As with TCP scans, receiving a response packet indicates that the port is open.
What is the difference between TCP and UDP scan?
Connectionless protocols ( UDP ) spread the state required to carry the data through every possible device while a connection oriented protocols ( TCP ) constrains the state to only those that are involved in the two-way communication process. …
What protocol is used for port scanning?
TCP
The general protocols used for port scanning are TCP (transmission control protocol) and UDP (user datagram protocol). They are both data transmission methods for the internet but have different mechanisms.
Which port is easiest to hack?
Commonly Hacked Ports
- TCP port 21 — FTP (File Transfer Protocol)
- TCP port 22 — SSH (Secure Shell)
- TCP port 23 — Telnet.
- TCP port 25 — SMTP (Simple Mail Transfer Protocol)
- TCP and UDP port 53 — DNS (Domain Name System)
- TCP port 443 — HTTP (Hypertext Transport Protocol) and HTTPS (HTTP over SSL)
How are TCP and UDP protocols used in port scanning?
As previously mentioned, TCP and UDP are frequently the protocols used in port scanning. There are several methods of performing TCP scans: SYN scans, the most common form of TCP scanning, involve establishing a half-open connection to the target port by sending a SYN packet and evaluating the response.
Can a TCP / UDP header be in an IP fragment?
That is correct. IP fragments will contain only IP fields. The TCP/UDP header will be in the first fragment only. So, you’d have to collect the entire frame (from all the fragments) to apply any L4 rules to it, or track the entire session to apply the same rule to all the fragments.
How is IP fragmentation a problem for firewalls?
TCP or UDP header is only present in the first fragment. This makes it impossible for firewalls to filter fragment datagrams based on criteria like source or destination ports. A more elaborate description of IP fragmentation problems can be found in these articles by Geoff Huston:
How is the fragmentation of an UDP datagram controlled?
Fragmentation is controlled by the Identification, Fragment Offset, and More Fragments (MF) fields in the IPv4 header. The original UDP datagram included 2992 bytes of application (UDP payload) data and 8 bytes of UDP header, resulting in an IPv4 Total Length field value of 3020 bytes (IP header is 20-byte).