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Business Logic Flaws

Posted by Anton Aylward

Toronto - OWASP

This month's meeting was about layer 7 errors in web applications. Trey Ford was a fast spoken Texan and gave some good examples.

The common thread, as I saw it, was that no amount of pen testing, no amount of risk analysis would have uncovered these flaws. What they had in common was 'failure mode'. Its another FMEA situation. The designers were optimists and never conceived of the abuse and trickery that might be perpetrated.

Let me give another Layer 7 example.

One of the lists I belong to forbids Out-of-the-Office messages. If anyone is so foolish as to have one set up to respond to list messages he gets ridiculed on the list. If his message leaves other contact information, we'll contact those people and tell them of the mistake.

Other lists I'm on seem to suffer from what amounts to OotO broadcast storms. When I submit a post to them I get a flood of OotO messages that compares to my daily spam. Sending OotO response to a mailing list message is dumb in the first place, but its also a security issue. Some of these lists don't have restricted membership, so someone could join with the express intention of harvesting addresses or other inside information.

Even worse, try googling for "out of the office". Its amazing how easy social engineering can be.

Your company may mandate the use of OotO, but its most useful internally and should not be used in response to mailing lists. If you are going to use this mechanism make sure you have it set up properly.

Back in 2003, my German friend and fellow CISSP, Axel Eble, wrote a draft RFC about OotO best practices. Sadly it died without becoming an IETF baseline.

See also:
'Out of office' messages turned into spam relays

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