diff --git a/checktrust/lightdm-greeter-wrapper b/checktrust/lightdm-greeter-wrapper
new file mode 100755
index 0000000..1e47ada
--- /dev/null
+++ b/checktrust/lightdm-greeter-wrapper
@@ -0,0 +1,3 @@
+#! /bin/bash
+(/usr/libexec/lightdm-show-trust-warning &)
+exec "$@"
diff --git a/checktrust/lightdm-show-trust-warning b/checktrust/lightdm-show-trust-warning
new file mode 100755
index 0000000..ed738c0
--- /dev/null
+++ b/checktrust/lightdm-show-trust-warning
@@ -0,0 +1,28 @@
+#! /usr/bin/bash
+
+while true; do
+    reply="$(/usr/sbin/checktrust)"
+    if [ "$reply" = "trusted" ]; then
+        break
+    elif [ "$reply" = "not trusted" ]; then
+        if [ -z "$XDOPID" ]; then
+            (while true; do xdotool search --sync --name bla windowraise; sleep 1; done) &
+            XDOPID=$!
+        fi
+        xdotool search --sync --name bla windowraise &
+        zenity --width 400 --error --title bla --text \
+"<b>Loss of trust detected!</b>
+
+Looks like your machine lost the trust of our network. Maybe it was offline for too long.
+
+<i>You won't be able to log in.</i>
+
+<b>Please contact IT Helpdesk</b>
+
+helpdesk@molgen.mpg.de
+phone: -1708"
+        continue
+    fi
+    sleep 5
+done
+test -n "$XDOPID" && kill $XDOPID
diff --git a/checktrust/lightdm-use-wrapper.conf b/checktrust/lightdm-use-wrapper.conf
new file mode 100644
index 0000000..80af383
--- /dev/null
+++ b/checktrust/lightdm-use-wrapper.conf
@@ -0,0 +1,2 @@
+[Seat:*]
+greeter-wrapper=/usr/libexec/lightdm-greeter-wrapper
diff --git a/install.sh b/install.sh
index 5887a97..11475d2 100755
--- a/install.sh
+++ b/install.sh
@@ -167,4 +167,8 @@ install_data crashkernel/crashkernel.service              "$DESTDIR$systemdunitd
 install_exec crashkernel/crash-recovery.sh                "$DESTDIR$root_sbindir/crash-recovery.sh"
 install_data misc_systemd_units/admin-sshd.service        "$DESTDIR$systemdunitdir/admin-sshd.service"
 install_exec checktrust/checktrust                        "$DESTDIR$usr_sbindir/checktrust"
+mkdir -p "$DESTDIR$sysconfdir/xdg/lightdm/lightdm.conf.d"
+install_data checktrust/lightdm-use-wrapper.conf          "$DESTDIR$sysconfdir/xdg/lightdm/lightdm.conf.d/50-use-wrapper.conf"
+install_exec checktrust/lightdm-greeter-wrapper           "$DESTDIR$usr_exec_prefix/libexec/lightdm-greeter-wrapper"
+install_exec checktrust/lightdm-show-trust-warning        "$DESTDIR$usr_exec_prefix/libexec/lightdm-show-trust-warning"
 exit