Hi,
Now that I'm keeping a watch, imagine my surprise when both my programs show download activity without a single browser window open and fetchmail having been killed !!
How do I find out what is being downloaded ? or what program is the guilty one ?
$ netstat -ntpa
btw, a. The hacker theory is not too far fetched ...although, i'll make no comments of the ability of MTNL folks to figure that out as a _definite_ reason. b. With what you've mentioned about it is possible that you have some background updates or some such thing. c. The last (and a bit unlikely ...tho' plausible) explanation is a faulty driver update or a faulty NIC. For example, in such cases, you'd have an increase in overhead traffic like unnecessary RSTs or dup ACKs etc ...it is not common but it is possible. Here tcpdump is your best bet to capture (and hopefully understand) what is happening.
cheers, - steve