Re: [Asrg] Countering Botnets to Reduce Spam

[Chris Lewis <[e-mail]>]

On 12-12-14 08:39 AM, Rich Kulawiec wrote:

> - Linux systems are not a significant component of botnets.  I've been
> doing passive OS fingerprinting for most of a decade, and they're in
> the noise floor.  It's still true now, as it was years ago, that
> bot-originated spam comes from Windows systems to about six 9's.

If only that were still true.  Sorry Rich.

Compromised Linux machines (mostly servers) are now responsible for ~40%
of all spam.

The actual _count_ of compromised Linux machines is indeed quite low.
Say 62K out of 8.6M observed compromised machines.  About .72%. Two 9's ;-)

But prolific?

I have individual IPs out in the wild that have shoved >1M spams into a
single trap in <48 hours.  I have a copy of one of these bots.  I
periodically run it on a wimpy dual-Atom linux laptop to characterize
what it's sending at the time.  It shoves 65 spams per _second_.

Imagine what a real server could do on industrial grade connections.

And the machine owners don't notice!

> - Better techniques already exist, such a firewalling outbound port 25
> by default and only punching holes for systems that actually need to
> send mail.  Another example: monitoring the TCP connection rate to
> port 25 on remote systems -- spam-senders are likely to push it much
> higher than "normal".

Unfortunately,, getting people to deploy those is worse than pulling teeth.