Some suspicious software making request to nmcheck.gnome.org

nmcheck.gnome.org is not malware. It is the gnome network manager connectivity check (for captive portals/hotspots). Click the link and you will see a single text file with a text in it. It should be "NetworkManager is online".

Check /etc/NetworkManager/NetworkManager.conf. There probably is a section with this in it:

[Connectivity] 
uri=http://nmcheck.gnome.org/check_network_status.txt

nmcheck.gnome.org is a host used by NetworkManager to verify that it has Internet connectivity. gnome.org is owned by the Gnome project. This is not a suspicious domain.

nmcheck.gnome.org hosts a single file; network_status.txt, which indicates that NM is actually connected to the Internet.

In short, nothing to worry over.