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Port 121 Details

known port assignments and vulnerabilities
threat/application/port search:
Port(s) Protocol Service Details Source
121 tcp erpc trojans/backdoors that use this port:
Attack Bot (files: Sysadmin.exe-181KB, Mpeg.exe, affects Windows 9x/ME)
God Message (ports 80,121,7777, a.k.a. BackDoor.AB.gen, JS.Trojan.WindowBomb, affects Windows 9x/ME/NT/2k)
JammerKillah (files:, Jammerkillah.exe, Mswin32.drv, affects Windows 9x/ME)
BO jammerkilla

Encore Expedited Remote Pro.Call (IANA official)
121 tcp trojan Attack Bot, God Message, JammerKillah Trojans
121 tcp AttackBot [trojan] Attack Bot SANS
121 tcp GodMessage [trojan] God Message SANS
121 tcp JammerKillah [trojan] JammerKillah SANS
121 tcp JammerKillah [trojan] Jammer Killah SANS
121 udp erpc Encore Expedited Remote Pro.Call Nmap
121 tcp,udp erpc Encore Expedited Remote Pro.Call IANA
8 records found
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External Resources
SANS Internet Storm Center: port 121

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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