Is log_in_vain really good or really bad?

[D J Hawkey Jr]

On Apr 17, at 04:28 PM, z3l3zt at hackunite.net wrote:
> 
> Heya..
> 
> Yesterday someone "attacked" by box by connection to several ports.. In
> other words, a simple portscan.. yet, since my box has "log_in_vain"
> enabled, so it tries to log everything to /var/log/messages, since the
> logfile got full and the size went over 100K, it tried to rotate the log
> to save diskspace.
> 
> (Apr 16 21:00:00 omikron newsyslog[32137]: logfile turned over due to
> size>100K)
> 
> My server box is a Intel Celeron 733Mhz, 384Mb of RAM.. yet it's slow from
> time to time since I only run ATA66 due to the old motherboard. When this
> "attack" occured yesterday, the box almost died and the box were working
> 100%.. all users who were logged in got "spammed" since the default
> *.emerg in /etc/syslog.conf is set to "*" ..

If you're running a relatively slow bus, chances are you could (maybe
even "have"?) experienced this already by a completely different set
of circumstances, but didn't put it together?

> Isn't this a quite simple way of making a DoS attack against a system? My
> box is running on 10mbit and the person who scanned my server were
> connecting from a cable connection...
>          [SNIP]

Assuming the attacker knew you had a slower bus, were running FreeBSD,
had log_in_vain turned on, and ... ? 

> I would be glad if anyone could tell me how to solve this and/or how to
> make sure it doesn't happen again.

Seems to me you're hampered by your hardware, and this episode is/was
just the latest symptom.

Moving /var to another physical drive on a different channel will help.
So would tuning /etc/syslog.conf. Of course, so would turning off the
log_in_vain knob (though I like it on, too). A new ATA adapter isn't all
that expensive anymore, and would boost performance overall.

HTH,
Dave

-- 
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