On 11/27/2017 02:02 PM, m.roth at 5-cent.us wrote: > Pete Biggs wrote: >> - don't run ssh on 22, use a different port. > I consider that pointless security-through-obscurity. Security through obscurity it may be, but it isn't pointless. Tarpits are in a similar class; they don't help with security in the absolute sense, but they slow the attacker down, and that might be enough to prevent the attack from continuing. (that is, put a tarpit on port 22 and run the real ssh elsewhere!) Any and all stumblingblocks you can put in the attacker's way, whether they're 'real' security or not, are worth at least looking at and evaluating their usefulness. Port knocking is an extreme form of security through obscurity, in reality, and falls into this class of tools. Likewise fail2ban; all it really does is slow down the attacker. No, obscurity-increasing tools will not stop the determined attacker, but, it is very true that these sorts of measures can and do increase the signal-to-noise ratio in your logs; what does get logged will likely be much more useful and indicative of a more determined attacker. Anything that substantially increases the log's signal to noise is useful and not pointless, in my opinion. Anything that slows down the attack is even more useful. I actually have training as a locksmith, with a specialty in masterkeying systems like rotating-constant and some obscure variations of RCM (this is one of the two masterkey systems explored in the infamous (in locksmith circles) paper "Cryptology and Physical Security: Rights Amplification in Master-Keyed Mechanical Locks" by Matt Blaze [1] [2]). In physical security all security is, in reality, through obscurity [3] (page 2, first paragraph): things like keeping the drill points secret (example: in a pin-tumbler lock, if you can drill the shear line, you are in; but what if you have extra pins and hidden shear lines?), keeping secret what materials are used for the hardplate and their interactions with commonly-available drill-bit materials [4], having a strategically placed and hidden tear gas vial [5], etc (all of this information is publicly available; I'm not spilling any real locksmith secrets here). The real key to effective physical security is not keeping the attacker out in an absolute, 'can't possibly break in' sense, but buying time for response to the attack; as the attack continues to eat time, the attacker will have increasing incentive to leave the premises. Now, if you want a real eye-opener about physical security, grab a copy of "OPEN IN THIRTY SECONDS" from Amazon [6]. That and the key reference, Marc Weber Tobias' LSS (Locks, Safes, and Security [7]) are fascinating (if expensive) reading and great resources for the syadmin who wants to dig into what is really meant by a security mindset. [1]: http://www.crypto.com/papers/mk.pdf [2]: http://www.crypto.com/masterkey.html [3]: http://www.crypto.com/papers/safelocks.pdf [4]: https://reassembler.wordpress.com/2008/02/04/drilling-into-a-modern-safe/ [5]: http://www.lockpicking101.com/viewtopic.php?f=8&t=16891 [6]: https://www.amazon.com/OPEN-THIRTY-SECONDS-Cracking-America/dp/0975947923 [7]: https://www.amazon.com/Locks-Safes-Security-International-Reference/dp/0398070792