Port 3127MyDoom Backdoor

TCP 3127 is known as a legacy MyDoom backdoor; IANA separately assigns the port as CTX Bridge Port.

transport: tcp · udp
in transit: cleartext
assignment: official
risk: 7/10
lookups: 0

also known as ctx-bridge, CTX Bridge Port

Technical Details

what runs on :3127

IANA assigns TCP and UDP 3127 the name ctx-bridge and the description “CTX Bridge Port,” but that entry does not establish a public protocol with a defined handshake or framing. The port is also known historically for the MyDoom worm’s TCP backdoor listener, which used a malware-specific protocol rather than a standard service protocol. Do not infer that an ordinary CTX Bridge service is present just because this port is open.

Security Information

exposure of :3127

risk score

7/ 10risk

treat as sensitive. widely scanned and regularly exploited when reachable — restrict it to known sources.

security averages 3.1 across 350 ports — this one sits 3.9 above.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp · udp

udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite

security overview

The historical MyDoom listener provided a remote-access path to an infected host; it is not a service that should be exposed to the internet. If TCP 3127 is unexpectedly open, identify the listening process and investigate the host for compromise rather than assuming it is the IANA-registered service. The malware use is legacy, and the available scan data does not show this port open.

Record

iana registry entry

port: :3127
service: MyDoom Backdoor
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 7/10risk
category: Security
usage: This is not a broadly used general-purpose service. Historically, MyDoom infections opened a TCP listener on port 3127 for backdoor access; an unexpected listener should be investigated as possible malware or an unknown application. The IANA ctx-bridge assignment is separate from this documented use.
lookups: 0rank 993
added: 2026-09-27
updated: 2026-09-27
references: IANA service name registry — port 3127

Something wrong?

This record is maintained by the engineers who use port 3127. Every field on it is editable — change what's wrong, say how you know, and a reviewer publishes it, usually within a minute. Last touched 2026-09-27.

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Related Ports

all 350 in security →

the 8 most looked-up other ports in security — 350 ports carry that label.

port	service	proto	category	risk	views
:8881	Atlasz Secure Server	TCP	Web Services	caution	67.6k
:443	HTTPS	TCPtls	Web Services	caution	65.9k
:8291	Winbox MikroTik Admin	TCP	Security	caution	62.9k
:3268	Microsoft Global Catalog (GC)	TCPUDP	Security	caution	54.6k
:135	Microsoft EPMAP	TCPUDP	Security	caution	51.9k
:3128	Squid Proxy HTTP	TCP	Web Services	caution	45.8k
:8080	HTTP Alternate	TCP	Web Services	caution	44.9k
:7000	Vuze HTTPS Tracker	TCPtls	Security	caution	28.9k

risk mix of the 8 listed

caution100%

2 of 8 encrypted

Port :3127MyDoom Backdoor

Technical Details

Security Information

Related Ports

Port 3127MyDoom Backdoor