I discovered an instance of dnsmasq running on my fresh install of xubuntu desktop. The general purpose of dnsmasq is known to be a DNS relay and DHCP server. The running process is reported as follows:
/usr/sbin/dnsmasq --no-resolv --keep-in-foreground --no-hosts --bind-interfaces --pid-file=/var/run/sendsigs.omit.d/network-manager.dnsmasq.pid --listen-address=127.0.0.1 --conf-file=/var/run/nm-dns-dnsmasq.conf --cache-size=0 --proxy-dnssec
Looks like it is spawned by network-manager. Contents of mentioned files are:
#cat /var/run/nm-dns-dnsmasq.conf
server=192.168.2.1
In my local network 192.168.2.1 indeed is a DNS server.
I cannot understand why this instance of dnsmasq listens on 127.0.0.1 since I see no way to serve DNS relay and DHCP server on 127.0.0.1 interface.