have been wondering about this,as i have read on here,people who knew who the person was who hired the assassin? there never seems to be any record on the letter (from the dead assassin) whom hired them?not that my character holds a grudge you understand,she just wants to help rid the world of naer do wells

if its a Dark Brotherhood assassin, then its astrid.

ah! had no idea it was one person (had to google astrid/sorry that sounded rude i didn't know who she was (have no dealings with the dark brotherhood

There is nobody behind the assassin. It's just a random encounter.

Astrid only dispatches the assassin. As to who actually prays for the contract...that's unknown.

From a gameplay point of view, yes it is simply a random encounter.
From a lore/story stand point I would say that it is someone that dislike you(In Tynons case it is a nobleman from Daggerfall), but you will never know because the DB are good at keeping secrets from others.

I may be wrong, but I could have sworn early in the game before patches, those letters used to say who they were from.

Or its hired thugs that have letters that say who they are from. Astrid keeps dispatching assassins for my lv43 Orc... she should start sending more then one at a time if she wants to be successful.

The last time Hired Thugs came after me, they had a letter warning them that I was a challanging target and to proceed with caution and that the employer (who was named) was not responsible for injuries should they fail.

Well they failed and I hunted down that old hag in that hut outside Riverwood and killed her. Her name was the employer.

Thugs carry letters of instruction, and the author can vary. It's always somebody you wronged. Kill Anise, and you may be attacked by thugs. Steal from her hut, though, guarantees a hit job. I've even been attacked by thugs sent by a bandit! Then there are the necromancers who carry a note instructing them to kill anybody possessing Azura's Star.

The thugs are usually from people you've commited crimes against, bit odd if they didn't see you steal that dinner set though i think the assasins are just random.

It's even odder when you kill someone and they send a hit squad against you. I just got one from Anise and I know she is sleeping with the fishes...

There's a way to stop this random encounter form happening, actually two: joining the DB or ending their presence in Skyrim

I've gotten the assassins on every single one of my characters, both goody two shoes, and the scum of the Earth Nirn. If it's a random encounter, it's not very random, or there just aren't very many in Skyrim anyway. As for the hired thugs, I find it funny that I can kill in cold blood every one of the Vigilants of Stendarr at their base of operations and get no thugs after me for it, but should I steal a plate from them, then they take offense and send their precious thugs to be killed by me. Seems like justice in Skyrim is a bit wonky.

Usually it should say someones name like, if you steal from Jarl Balgruff the Greater it should say that on the letter like something like. "Our contact Jarl Balgruff the Greater has paid good coin for this assassination. Do not fail me" or something