SMTP File Hash not consistent

Hi All!

First off… I’m kinda new to Bro so please be gentle….

I’ve noticed some issues (strangeness?) with the file logging on Bro, in particular I would like for Bro to log an MD5 for all incomming files sent in through SMTP. At the moment it only seems to do it for some files and I can’t seem to find a reason why some are getting hashed but others aren’t…

An extract from my files.log filtered by SMTP and pdf:

1449167625.904080 FS81ev 1449167623.516100 Fajnj71Xx6UprSmLef 198.22.115.26 208.33.144.195 C6pKQN2extOHQYZ4Fc SMTP 3 SHA1,MD5 application/pdf LoadTender3059527.pdf 0.015949 F T 57 - 1368 0 F - - - - -

1449167625.848077 FhU87R1PwGYciZcT2i 198.22.115.26 208.33.144.195 CkD4rQ1uG5VZhJL2v9 SMTP 1 SHA1,MD5 application/pdf 12.03.2015.pdf 0.016022 F T 456 - 1368 0 F - - - - -3MhA2vXGk5J8 198.22.115.26 208.33.145.195 CHB8Ew4kdUB3hDbkKl SMTP 3 SHA1,MD5 application/pdf Payment Advice Note from 12/03/2015.PDF 0.071983 F T 14535 - 0 0 F - ef853cc031d2abfbf6e0ec964163cd98 08eae5d275554f12d4783cb9c8be210d691f8db5 - -

1449167630.224049 FGUsvz3nDYqZlH56Y1 198.22.115.26 208.33.145.195 CK8Nwn4vGwpylAmpGj SMTP 3 SHA1,MD5 application/pdf PPC_LoadTender3057660.pdf 0.032006 F T 969 - 1544 0 F - - - - -

1449167631.024050 FiMmk5Zsczli9OGi7 198.22.115.26 208.33.144.195 CX4SUd3VDBBdYoXt0g SMTP 3 SHA1,MD5 application/pdf Payment Advice Note from 12/03/2015.PDF 0.011997 F T 171 - 1368 0 F - - - - -

So basically about it won’t create a file hash for a heap of file, then out of the blue it will create one, then no more for a while….

They all have the same mime type so I just can’t seem to figure this out… any help or advice would be really appreciated…

Cheers,

David.