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Saturday, January 26, 2013

Comments on ICS CERT ICS-ALERT-13-016-02

There is a flame in media about our S7 bruteforce tool

Just for instance:  "...and have unfortunately made the code available before the Siemens had the opportunity patch the flaw or offer mitigations..." (src =
C'mon, guys, you serious? Mitigation against offline bruteforce in password-based authentication? Maybe you should take a lessen or two on information security?

1.    There are no any security vulnerability disclosed by released tool. SHA-1 and HMAC-SHA-1 crypto implementation in S7 according our analysis strong enough. No salt? May be...
2.    Issue related to S7 password known for a while and documented on Siemens site. Prooflink:;51401544;2.x=34&switchLang;51401544;2.y=4&lang=en&siteid=cseus&aktprim=0&objaction=csopen&extranet=standard&viewreg=WW
3.    Published tool (and JtR plug-in) require valid challenge-response packets, so risk of potential abuse is very low because attacker need to intercept communications before.
4. It's hard to use Rainbow Tables. Because of challenge-response attacker need to spoof challenge, e.g. to mount MITM attack in adjacent network.

Thus we agree with Siemens, they don't need to release a patch (src =

PS. Yes, we know a bit about SSL. Prooflink:

PPS. Yes, there are situations where  you don't need to brute HMAC-SHA-1 to get S7 password. But...

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