SSH Password Gropers Are Now Trying High Ports

badger.foo writes "You thought you had successfully avoided the tiresome password guessing bots groping at your SSH service by moving the service to a non-standard port? It seems security by obscurity has lost the game once more. We're now seeing ssh bruteforce attempts hitting other ports too, Peter Hansteen writes in his latest column." For others keeping track, have you seen many such attempts?

Comments

Low Hanging Fruit

[Nerdfest]

It's still just going after low-hanging fruit. Anyone weth any real awareness of security does now allow password-only SSH connections anyway. Key based auth and fail2ban is pretty much required these days. You can always add some port knocking to obscure it a bit if you don't like reading about failed access attempts.

Re:Low Hanging Fruit

[DaveAtFraud]

I've been using key based authentication for ssh for years. I just moved the service to a high port to get rid of all the script kiddy password guessing attempts that were clogging my log file. I also added a "throttle" in iptables:

# Block brute force attacks
# Drop repeated ssh connection attempts within 20 seconds interval
-A INPUT -p tcp -m tcp -m state -m recent -i eth1 --dport 22222 --state NEW -j DROP --rcheck --seconds 20 --name THROTTLE --rsource

# Accept ssh connection if not attempted within past 20 sec.
-A INPUT -p tcp -m tcp -m state -m recent -i eth1 --dport 22222 --state NEW -j ACCEPT --set --name THROTTLE --rsource

It just cuts down on the noise. I used the same technique back when people were doing the DNS cache poisoning attacks to limit how many hits my DNS could get from the same source (first query should update the cache in a legitimate site's DNS so no reason why I should get repeated hits from the same site).

Cheers,
Dave

Re:Low Hanging Fruit

[larry bagina]

Just think -- if it was open source, you could submit patches to make it more effective. They're basically fucking themselves over by keeping it closed source.

Dumbass parroting.

[Anonymous Coward]

It seems security by obscurity has lost the game once more.

How, exactly?

By ensuring the vast majority of brute force attacks - which hit port 22 - fail?

Security isn't fucking binary, and obscurity is a perfectly valid layer of the onion.

Re:Dumbass parroting.

[astralagos]

Security through obscurity is one of the most spectacularly misunderstood concepts in information security, partly because it's gotten confused with open source politics. The core concept behind it (Kerckhoffs' principle) is best stated as "assume that the enemy knows your system as well as you do". In cryptosystems this means that the secret is a controlled and limited entity - the key. The key must -still- be hidden and controlled, but Kerckhoff's principle ensures that you have only one thing to have to control. Various federal agencies used to, for example, assume that the first version of any cryptosystem they sold would be bought by Moscow and rapidly analyzed.

Well and good, but all any security implementation buys you is *time*. The real problem with StO is that the time it buys you is unpredictable, and in Kerckhoffs' era of large and slow system upgrades, it might take years to update a cryptosystem once it was broken. Malware authors have happily used StO for years -- for example, evading detection mechanisms by using a number of off the shelf packers in sequence. The approach works because they replace their malware faster than anyone figures out the packing sequence. The windtalkers during WWII were a security through obscurity approach, and it worked fine for the duration of the war, but would have gone horribly in the next one.

Now, what we're dealing with here is network defense, which isn't crypto. In network defense, creative lying is enormously helpful because you can use it to differentiate between your ignorant attackers and knowledgeable members of the community. The majority of attackers scan horizontally (all hosts on a fixed number of ports) rather than vertically (all ports on a number of hosts) because vertical scanning is a waste of time. Most attackers normally hit 9-10 ports and then move onto the next potential target -- they don't see the network in terms of what the hosts *are*, just what they can *exploit*. Moving SSH to a random port means that the attacker now has to spend 6000x the effort to figure out of there's anything on the host he cares about, and he's probably not going to bother when there are nice sysadmins out there happy to put everything on port 22 (as always, I don't have to outrun the bear. I just have to outrun you.) Copy it with some aggressive port blocking (like port 22) or a threshold random walk scan detector and you've got a perfectly fine way to ignore idiots. It's also worth noting that the mentioned port is 2222, which tends to be "stupid port manipulation rule #2" among folks (the other one being to add 1 in front of the port numbers, I can't tell you how fascinating it was to watch port 16888 the first time we blocked bittorrent).

Re:Just lock em out...

[msauve]

If you lock out the account, and not the incoming host, then you simply provide a DoS mechanism to lock out legitimate users.

I do security by antiquity

[Anonymous Coward]

You see, I don't use SSH, I use plain old telnet. That's right! These kiddies never heard of it!

And if they actually get in, I have a few gigabytes of stories growing up that they have to read. Like the time I was growing up in Idaho. We wore onions on our belts because that was the style back then, Benny Goodman was all the rage and I'd take my best girl - Betsy - to the church dance ... we were all Presbeterian in that town and with one church, new people would just go there - even the Jews because there wasn't a Synagogue - but that's another story and I won't bore you with that because I can be a bit long winded at my age - so anyway my best girl got her new dress and we over to the next town to Jo's soda shop - he had the BEST malts in the entire area - and the whipped cream was made fresh from a local dairy farm - farmer brown's was his name - he served in WWI as an infrantry man in France and boy the stories he told about those French girls - like the one he met, Jaquoline I think or it was Juliette - she had dark hair and hazle eyes and her father was a banker for a German who had a home in France before the war - of course when the war started the Germen businessman had to run home and he ended fighting himself, even though his father pulled some mighty strings to get him out of the German army ...ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ

Re:Don't rely on security-though-obscurity

[AmiMoJo]

You might as well expire those banned IP addresses after a day because 99.97% of them are compromised machines on dynamic connections. Having a file that size just wastes computing resources (having to check every single one) and slightly increases the chance you won't be able to log in from some random place one day.

Re:No I haven't, and here is why:

[Anonymous Coward]

I've setup port-knocking to open the port I actually use for SSH, and my SSH key is passphrase protected. Passphrase not password.

Pfft. Lightweight. Nobody's ever getting into my passnovelseries-protected pubkey. Passnovelseries not passnovel.

And I change languages and character sets every chapter.