a certain time, the X server presumes that the display manager has ceased running, and can terminate the connection. Security One problem with XDMCP is that, similarly to telnet, the authentication takes place unencrypted. If snooping is possible, this leaves the system vulnerable to attack. It is more secure to use an ssh tunnel for X traffic. Implementations The X Window System supplies XDM as its standard display manager. Programmers have developed other X display managers, both commercial and free, offering additional functionality over the basic display management: Active GDM, GNOME implementation SDDM, recommended display manager for KDE Plasma 5 and LXQt. Successor to KDM. LightDM, a lightweight, modular, cross-desktop, fully themeable desktop display manager by Canonical Ltd. TWin, the TDE window manager xlogin display manager, a lightweight, secure and login like console display manager for X, written in C. Inactive KDM (part of KDE) allows the user to graphically select a window manager or desktop environment in the login screen Qingy ultralight and very configurable graphical login independent on X Window (uses DirectFB) XDM-OPTIONS for XDM. Easy full install, Xhost Phonebook, X Login, X Desktop Chooser, menu-reconfig, repair utils. LDM, the (remote) Display Manager of the Linux Terminal Server Project MDM, a graphical display manager developed for Linux Mint. dtlogin (shipped with CDE) (provided by SCO Open Desktop) also checks for expired passwords and performs some administrative tasks WINGs Display Manager (using the WINGs widget-set used in Window Maker) entranced/entrance (employs the architecture used in Enlightenment v.17, on hiatus since 2005) LXDM, a lightweight cross-desktop and fully themeable display manager, part of LXDE SLiM, an independent login manager. CDM, an ultralight Console Display Manager for Unix xlogin, X Window login with separate XDMCP server Enter, a lightweight graphical login manager Orthos, another lightweight solution with very configurable animated themes that use OpenGL only nodm, auto-login display manager for systems like kiosks, appliances and mobile phones On some Unix distributions, the default display manager is selected in file $PREFIX/etc/X11/default-display-manager. See also Login manager X Window System protocols and architecture Sources XDMCP specification, from the X.Org release documentation XDM manual page (XFree86.org) Linda Mui and Eric Pearce, X Window System Volume 8: X Window System Administrator's Guide for X11 Release 4 and Release 5, 3rd edition (O'Reilly and Associates, July 1993; softcover ) References External links Linux XDMCP HOWTO Taming The X Display Manager The X Display Manager, from the FreeBSD