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Port 143 Details

known port assignments and vulnerabilities
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Port(s) Protocol Service Details Source
143 tcp,udp IMAP IMAP (Internet Mail Access Protocol) mail server uses this port. See also port 993/tcp.

Numerous IMAP servers have buffer overflows that allow compromise during the login. Note that for awhile, there was a Linux worm (admw0rm) that would spread by compromising port 143, so a lot of scans on this port are actually from innocent people who have already been compromised. IMAP exploits became popular when Red Hat enabled the service by default on its distributions. This port is also used for IMAP2, but that version wasn't very popular. Several people have noted attacks from port 0 to port 143, which appears to be from some attack script.

MailServer.exe in NoticeWare Email Server allows remote attackers to cause a denial of service (application crash) via a long string to IMAP port (143/tcp).
References: [CVE-2008-1713] [BID-28559] [SECUNIA-29629]

Format string vulnerability in the University of Washington (UW) c-client library, as used by the UW IMAP toolkit imap-2007d and other applications, allows remote attackers to execute arbitrary code via format string specifiers in the initial request to the IMAP port (143/tcp). NOTE: Red Hat has disputed the vulnerability, stating "The Red Hat Security Response Team have been unable to confirm the existence of this format string vulnerability in the toolkit, and the sample published exploit is not complete or functional." CVE agrees that the exploit contains syntax errors and uses Unix-only include files while invoking Windows functions.
References: [CVE-2009-0671] [BID-33795]

ADM trojan also uses this port (TCP).
143 tcp,udp Internet Message Access Protocol (IMAP) - used for retrieving, organizing, and synchronizing e-mail messages (official) Wikipedia
143 tcp trojan ADM worm Trojans
143 tcp,udp applications Imap Portforward
143 tcp,udp imap Interim Mail Access Protocol v2 Nmap
143 tcp,udp imap Internet Message Access Protocol [RFC3501] , modified: 2017-06-05 IANA
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Related ports: 25  110  993  8143  

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External Resources
SANS Internet Storm Center: port 143

Port numbers in computer networking represent communication endpoints. Ports are unsigned 16-bit integers (0-65535) that identify a specific process, or network service. IANA is responsible for internet protocol resources, including the registration of commonly used port numbers for well-known internet services.
Well Known Ports: 0 through 1023.
Registered Ports: 1024 through 49151.
Dynamic/Private : 49152 through 65535.

TCP ports use the Transmission Control Protocol, the most commonly used protocol on the Internet and any TCP/IP network. TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and that packets will be delivered in the same order in which they were sent. Guaranteed communication/delivery is the key difference between TCP and UDP.

UDP ports use the Datagram Protocol. Like TCP, UDP is used in combination with IP (the Internet Protocol) and facilitates the transmission of datagrams from one computer to applications on another computer, but unlike TCP, UDP is connectionless and does not guarantee reliable communication; it's up to the application that received the message to process any errors and verify correct delivery. UDP is often used with time-sensitive applications, such as audio/video streaming and realtime gaming, where dropping some packets is preferable to waiting for delayed data.

When troubleshooting unknown open ports, it is useful to find exactly what services/processes are listening to them. This can be accomplished in both Windows command prompt and Linux variants using the "netstat -aon" command. We also recommend runnig multiple anti-virus/anti-malware scans to rule out the possibility of active malicious software. For more detailed and personalized help please use our forums.

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