UDP 177
Synopsis
- UDP port 177 is used by the X Display Manager Control Protocol (XDMCP).
- It’s implemented by display managers such as xdm (X.Org), GNOME Display Manager (GDM), KDE’s KDM, and LightDM to provide remote graphical login.
- Commercial/enterprise Unix systems historically used it via CDE’s dtlogin on Solaris and HP-UX.
- Thin-client and X-terminal deployments (e.g., older LTSP setups and hardware terminals from Wyse/NCD) use UDP 177 to discover and connect to a display manager.
- Associated with exploitation: XDMCP is largely unencrypted and often probed; exposing UDP 177 can present a remote login prompt and enable credential sniffing or unauthorized access, so many systems disable or tightly restrict it.
Observed activity
Last 30 days
Detailed chart