Re: [clamav-users] Odd behavior when scanning eicar test files

Haukur Valgeirsson via clamav-users Tue, 27 Apr 2021 02:56:57 -0700

Hi again.

Now I am getting really confused. I repeated the tests but now scanning the eicar files in different directories in the same scan. I compiled the file list into a file that I read into an array in bash and pass to clamscan. The results differ between directories, even if the files in them are identical (confirmed with diff).

The modified script is attached (clamcars2.sh), the file read in (testfiles.txt) is just a list of full path to the files. The results are in clamscan_eicar_test.txt, each part begins with the filename being md5 sum whitelisted.


Any help very much appreciated!

Best regards,

Haukur

On 26.4.2021 15:30, Haukur Valgeirsson via clamav-users wrote:

Uhm... now this is strange.
When I run the script I wrote, it behaves as one would expect (md5 sum must match the file, md5 from eicar.com covers eicar.com.txt too, but not the zips and the md5 from zips only covers the zip that it was generated from).
then I reran with the falsepos file only containing the md5 sum from eicarcom2.zip
# cat /var/lib/clamav/maldet_ignore_sigs.fp
e4968ef99266df7c9a1f0637d2389dab:308:eicarcom2.zip

then it seems to whitelist eicar.com as well as itself???

# clamscan .
When run /usr/local/maldetect/testfolder/clamcars.sh: OK
/usr/local/maldetect/testfolder/eicar.com.txt: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND /usr/local/maldetect/testfolder/eicar_com.zip: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND
/usr/local/maldetect/testfolder/eicarcom2.zip: OK
/usr/local/maldetect/testfolder/eicar.com: OK
/usr/local/maldetect/testfolder/result_eicar.com: OK
/usr/local/maldetect/testfolder/result_eicar.com.txt: OK
/usr/local/maldetect/testfolder/result_eicar_com.zip: OK
/usr/local/maldetect/testfolder/result_eicarcom2.zip: OK
/usr/local/maldetect/testfolder/.clamcars.sh.swp: OK

----------- SCAN SUMMARY -----------

Known viruses: 8539062
Engine version: 0.103.2
Scanned directories: 1
Scanned files: 10
Infected files: 2
Data scanned: 0.00 MB
Data read: 0.00 MB (ratio 0.00:1)
Time: 42.336 sec (0 m 42 s)
Start Date: 2021:04:26 10:14:50
End Date:   2021:04:26 10:15:33
and just to test again, I scan another folder, only containing the eicar files:
# ll /home/haukurv/www/testfiles
total 16
-rw-r--r-- 1 haukurv haukurv  68 Apr 26 05:30 eicar.com
-rw-r--r-- 1 haukurv haukurv 308 Apr 26 05:30 eicarcom2.zip
-rw-r--r-- 1 haukurv haukurv  68 Apr 26 05:30 eicar.com.txt
-rw-r--r-- 1 haukurv haukurv 184 Apr 26 05:30 eicar_com.zip


# clamscan /home/haukurv/www/testfiles
/home/haukurv/www/testfiles/eicar.com: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND
/home/haukurv/www/testfiles/eicarcom2.zip: OK
/home/haukurv/www/testfiles/eicar.com.txt: OK
/home/haukurv/www/testfiles/eicar_com.zip: OK

----------- SCAN SUMMARY -----------
Known viruses: 8539062
Engine version: 0.103.2
Scanned directories: 1
Scanned files: 4
Infected files: 1
Data scanned: 0.00 MB
Data read: 0.00 MB (ratio 0.00:1)
Time: 32.812 sec (0 m 32 s)
Start Date: 2021:04:26 10:29:16

End Date:   2021:04:26 10:29:48


I am getting a little bit confused here :-s

reg. Haukur


On 26.4.2021 15:04, Haukur Valgeirsson via clamav-users wrote:
Sorry, adding more details for reproducability.
My original idea was to use maldet, which uses clamscan so whitelisting and path exclusions need to happen in clamav, they don't seem to be passed on to clamscan.
Environment: 4.19.0-10-amd64 #1 SMP Debian 4.19.132-1 (2020-07-24) x86_64 GNU/Linux
The script clamcars.sh (attached) downloads, whitelists, scans and puts the results in "result_<filename>" for each of the eicar files. I can repeat with debug output redirected into the file if it helps.
I am using "clamscan" (used apt-get install clamav) not the daemon (clamdscan), so I do not seem to have clamconf:
# clamscan --version
ClamAV 0.103.2/26152/Mon Apr 26 06:04:28 2021
Would it help you to look into this if I installed the daemon scanner and repeated the test?
The only config I was able to locate is below.

Thanks.

Haukur


====

# cat /etc/clamav/freshclam.conf
# Automatically created by the clamav-freshclam postinst
# Comments will get lost when you reconfigure the clamav-freshclam package
DatabaseOwner clamav
UpdateLogFile /var/log/clamav/freshclam.log
LogVerbose false
LogSyslog false
LogFacility LOG_LOCAL6
LogFileMaxSize 0
LogRotate true
LogTime true
Foreground false
Debug false
MaxAttempts 5
DatabaseDirectory /var/lib/clamav
DNSDatabaseInfo current.cvd.clamav.net
ConnectTimeout 30
ReceiveTimeout 0
TestDatabases yes
ScriptedUpdates yes
CompressLocalDatabase no
Bytecode true
NotifyClamd /etc/clamav/clamd.conf
# Check for new database 24 times a day
Checks 24
DatabaseMirror db.local.clamav.net
DatabaseMirror database.clamav.net


On 26.4.2021 13:42, G.W. Haywood via clamav-users wrote:
Hi there,

On Mon, 26 Apr 2021, Haukur Valgeirsson via clamav-users wrote:
I am setting up daily scanning and was figuring out how to whitelist based on file signatures, and decided to use the eicar test files to tune the settings. Used 'sigtool --md5 eicarcom2.zip > falsepossigs.fp' to create the sig to whitelist and proceeded to run test scans and the results were a little surprising:
Given your description of what you did I'd struggle to reproduce it.
Please give full details of how you are running the scans, the exact
unaltered output as you see it, and the output of 'clamconf -n'.
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clamcars2.sh
Description: application/shellscript

./result_eicar.com

/home/haukurv/www/4443/index.nginx-debian.html: OK
/home/haukurv/www/4443/index.html: OK
/home/haukurv/www/4443/testfiles/eicar.com: OK
/home/haukurv/www/4443/testfiles/eicarcom2.zip: {HEX}EICAR.TEST.3.UNOFFICIAL 
FOUND
/home/haukurv/www/4443/testfiles/eicar.com.txt: OK
/home/haukurv/www/4443/testfiles/eicar_com.zip: {HEX}EICAR.TEST.3.UNOFFICIAL 
FOUND
/home/haukurv/www/html/index.nginx-debian.html: OK
/home/haukurv/www/html/index.html: OK
/home/haukurv/www/http/eicar.com: OK
/home/haukurv/www/http/eicar.com.txt: OK
/home/haukurv/www/http/eicar_com.zip: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND
/home/haukurv/www/http/eicarcom2.zip: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND
/home/haukurv/www/testfiles/eicar.com: OK
/home/haukurv/www/testfiles/eicarcom2.zip: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND
/home/haukurv/www/testfiles/eicar.com.txt: OK
/home/haukurv/www/testfiles/eicar_com.zip: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND

----------- SCAN SUMMARY -----------
Known viruses: 8539062
Engine version: 0.103.2
Scanned directories: 0
Scanned files: 16
Infected files: 6
Data scanned: 0.00 MB
Data read: 0.00 MB (ratio 0.00:1)
Time: 39.017 sec (0 m 39 s)
Start Date: 2021:04:27 04:19:51
End Date:   2021:04:27 04:20:30


./result_eicar.com.txt

/home/haukurv/www/4443/index.nginx-debian.html: OK
/home/haukurv/www/4443/index.html: OK
/home/haukurv/www/4443/testfiles/eicar.com: OK
/home/haukurv/www/4443/testfiles/eicarcom2.zip: {HEX}EICAR.TEST.3.UNOFFICIAL 
FOUND
/home/haukurv/www/4443/testfiles/eicar.com.txt: OK
/home/haukurv/www/4443/testfiles/eicar_com.zip: {HEX}EICAR.TEST.3.UNOFFICIAL 
FOUND
/home/haukurv/www/html/index.nginx-debian.html: OK
/home/haukurv/www/html/index.html: OK
/home/haukurv/www/http/eicar.com: OK
/home/haukurv/www/http/eicar.com.txt: OK
/home/haukurv/www/http/eicar_com.zip: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND
/home/haukurv/www/http/eicarcom2.zip: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND
/home/haukurv/www/testfiles/eicar.com: OK
/home/haukurv/www/testfiles/eicarcom2.zip: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND
/home/haukurv/www/testfiles/eicar.com.txt: OK
/home/haukurv/www/testfiles/eicar_com.zip: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND

----------- SCAN SUMMARY -----------
Known viruses: 8539062
Engine version: 0.103.2
Scanned directories: 0
Scanned files: 16
Infected files: 6
Data scanned: 0.00 MB
Data read: 0.00 MB (ratio 0.00:1)
Time: 33.673 sec (0 m 33 s)
Start Date: 2021:04:27 04:20:30
End Date:   2021:04:27 04:21:03


./result_eicar_com.zip

/home/haukurv/www/4443/index.nginx-debian.html: OK
/home/haukurv/www/4443/index.html: OK
/home/haukurv/www/4443/testfiles/eicar.com: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND
/home/haukurv/www/4443/testfiles/eicarcom2.zip: {HEX}EICAR.TEST.3.UNOFFICIAL 
FOUND
/home/haukurv/www/4443/testfiles/eicar.com.txt: OK
/home/haukurv/www/4443/testfiles/eicar_com.zip: OK
/home/haukurv/www/html/index.nginx-debian.html: OK
/home/haukurv/www/html/index.html: OK
/home/haukurv/www/http/eicar.com: OK
/home/haukurv/www/http/eicar.com.txt: OK
/home/haukurv/www/http/eicar_com.zip: OK
/home/haukurv/www/http/eicarcom2.zip: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND
/home/haukurv/www/testfiles/eicar.com: OK
/home/haukurv/www/testfiles/eicarcom2.zip: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND
/home/haukurv/www/testfiles/eicar.com.txt: OK
/home/haukurv/www/testfiles/eicar_com.zip: OK

----------- SCAN SUMMARY -----------
Known viruses: 8539062
Engine version: 0.103.2
Scanned directories: 0
Scanned files: 16
Infected files: 4
Data scanned: 0.00 MB
Data read: 0.00 MB (ratio 0.00:1)
Time: 32.591 sec (0 m 32 s)
Start Date: 2021:04:27 04:21:03
End Date:   2021:04:27 04:21:36


./result_eicarcom2.zip

/home/haukurv/www/4443/index.nginx-debian.html: OK
/home/haukurv/www/4443/index.html: OK
/home/haukurv/www/4443/testfiles/eicar.com: {HEX}EICAR.TEST.3.UNOFFICIAL FOUND
/home/haukurv/www/4443/testfiles/eicarcom2.zip: OK
/home/haukurv/www/4443/testfiles/eicar.com.txt: OK
/home/haukurv/www/4443/testfiles/eicar_com.zip: OK
/home/haukurv/www/html/index.nginx-debian.html: OK
/home/haukurv/www/html/index.html: OK
/home/haukurv/www/http/eicar.com: OK
/home/haukurv/www/http/eicar.com.txt: OK
/home/haukurv/www/http/eicar_com.zip: OK
/home/haukurv/www/http/eicarcom2.zip: OK
/home/haukurv/www/testfiles/eicar.com: OK
/home/haukurv/www/testfiles/eicarcom2.zip: OK
/home/haukurv/www/testfiles/eicar.com.txt: OK
/home/haukurv/www/testfiles/eicar_com.zip: OK

----------- SCAN SUMMARY -----------
Known viruses: 8539062
Engine version: 0.103.2
Scanned directories: 0
Scanned files: 16
Infected files: 1
Data scanned: 0.00 MB
Data read: 0.00 MB (ratio 0.00:1)
Time: 34.754 sec (0 m 34 s)
Start Date: 2021:04:27 04:21:36
End Date:   2021:04:27 04:22:11

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Re: [clamav-users] Odd behavior when scanning eicar test files

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