The HOSTS file (which has no file extension) found in c:\windows\system32\drivers\etc\HOSTS is a textfile that acts as a lookup database table to handle the way that certain web addresses are directed.
In your case you want any "pubmatic" web addresses to be misdirected so that they cannot phone home.
This is the Microsoft sample HOSTS file:
Code:
# Copyright (c) 1993-2009 Microsoft Corp.#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host
# localhost name resolution is handled within DNS itself.
# 127.0.0.1 localhost
# ::1 localhost
Here is the same file edited to misdirect any "pubmatic" addresses to the address 0.0.0.0 - which is nowhere on the internet - just a virtual black hole or localhost address on your PC.
Code:
# Copyright (c) 1993-2009 Microsoft Corp.#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host
# localhost name resolution is handled within DNS itself.
# 127.0.0.1 localhost
# ::1 localhost
0.0.0.0 ads.pubmatic.com
0.0.0.0 bid.pubmatic.com
0.0.0.0 haso.pubmatic.com
0.0.0.0 showads.pubmatic.com
0.0.0.0 track.pubmatic.com
0.0.0.0 image2.pubmatic.com
These addresses come from the first link on the following google search, with a fuller explanation of the hosts file, and further information.
LMGTFY