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The Wireshark Network Analyzer
One of our client's masqueraded IP was banned several times as the source of spam. The problem was how to check a lot of smtp traffic going through the gateway from the local networks.
One method of investigation was to check what's going through the router. Because of relatively complex infrastructure we choosed to monitor the smpt connections and also traffic itself. On the gateway we checked for suspicious messagess via content filter.
As we were unsure about the source of spam, we had to catch all the mail traffic which was then passed to the filter. But how to assemble whole smtp message on gateway? The tool called Wireshark (tshark) was very handy in this case.
for i in {0..4};
do
echo eth${i}
nohup tshark -i eth${i} -d tcp.port==25,smtp -f "port 25" -w /var/smtp/eth${i} -a filesize:9048576 &
done
The example above stores all the smtp (header+body) traffic to file. The file is named after the interface the traffic goes through.
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Following example will show you the actual size/usage in blocks for every directory in your active directory and it also sorts it out by size (in blocks).
# du -ks ./* | sort -n
1 ./inet
1 ./news
1 ./nfs
1 ./nis
1 ./opt
1 ./preserve
2 ./mail
3 ./vx
4 ./ld
4 ./statmon
...
53920 ./log
75183 ./ldap
245626 ./sadm
3336619 ./mps
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Author of the soundtrack for Invasion of the Body Snatchers, psychiatrist and jazz piano player. I accidentally found video from 1983 Berlin Jazz Fest where Zentlin was performing his Quiet Now song. Enjoy.
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Need to cipher data on your hard disk? You can use well-known open-source solution - TrueCrypt. Unfortunately, you can't use TrueCrypt to protect your boot disk (to encrypt OS itself).
Of cource - Microsoft offers BitLocker in Vindows Vista Enterprise/Ultimate, but this is the most expensive Vista flavour. Plus, Vista still requires to create a new non-encrypted partition on your boot disk for kernel with crypto-support loading.
You can use fx. PGP Whole Disk Encryption (which seems to be widely used solution). But then you have to pay price which almost equals the price of Windows XP system.
While browsing the net I've found free (but not open-source) alternative to encrypt my boot disk. The software is available for Windows and Linux. The CompuSec's software uses 256-bit AES algorithm.
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