Ask HN: How to minimize unwanted net usage by processes to a trickle?

Hi HN,

I have this problem sometimes of what seems like excessive Internet bandwidth usage. Sometimes I have to use a metered connection, so the issue becomes more important. Leaving aside things like malware (which may happen, and for which I do have anti-virus software installed), what are ways to reduce Internet usage (other than that directly initiated by the user) to a trickle, so as not to waste money? Thanks in advance for all answers.

I'll mention one way that I am exploring: NetBalancer for Windows. A friend also told me about nethogs for Linux. Not tried yet.