I with Anton on this, this is almost certainly the same worm(s) which any *nix admins will see filling up their logs (if they haven't take then necessary precautions). Strikes me as a little odd that anyone who doesn't know about basic SSH security precautions would bother installing SSH on their iPhone (I don't think it is installed as part of the breakout). For those that don't know, here are some sensible precautions for running SSH (on any system):
1. Don't use default, obvious or easily cracked passwords - in fact, wherever practical, use keys and disable password authentication.
2. Disable root access - even better, disable access for all users except those you specifically need to allow.
3. Don't allow SSH access for default or obvious usernames (e.g. root, apache, john).
4. Don't run SSH on the default port.
5. I can't think of any reason why you would need to run SSH on the default port, but if you do then looking into Fail2Ban or DenyHosts (I can't think of anything like this that would work on an iPhone).
6. Don't run SSH when you aren't using it. There is little point running SSH all the time on an iPhone as you need to have the screen unlocked for it to work - so unless you have it set to be permanently unlocked, you will generally have it to hand when you need to use SSH and can started and stopped as necessary.
I reckon that there is about as much chance of this being a dedicated iPhone worm as there of a current SSH work not including the default usernames and password for the iPhone (i.e. none). IMHO Jailbreaking an iPhone is about as much of a security risk as installing Linux on a computer - the biggest difference being that malware on an iPhone has access to your phone and could run up a massive bill - but that is an ever present risk with a mobile phone and could easily prevented if O2 and other providers provided means to limit your account (e.g. maximum spend of £20 a day/£50 a week/£100 a month would suffice for most - it would also have helped those early 3G Internet users who got bills of for £1000 or more for the first month before they realised how outrageously expensive it is).