s-bits disappear ?

[Bernd.Lehle () RUS Uni-Stuttgart DE (Bernd Lehle)]

Hello,

today I had a strange experience on an IRIX 5.3 system.

I realized that the normal bunch of mails from the states had not come
in overnight. I checked if sendmail was still running when I realized
that ps would not give me the information ("insufficient permision").
I tried to become root by "su" which also would not let me ("insuf-
ficient permission"). After a puzzling search I took the machine in
single user mode to shield off a possible attack.

The following investigation yielded: The s-bits of /sbin/ps, /sbin/su
and /bin/mail had disappeared. I thought of Trojan Horses and compared
the checksums with sum and MD5 against secure binaries on a different
system some place else. There was no difference.

So I am not sure if this was a hacking attempt or a OS bug.

Anyone seen this before ?

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