the bundle that is connected to the address you’ve posted shows that two of your addresses were affected: https://thetangle.org/bundle/FJVR9B9R9OWFHAHNKBXSYGJKYVBEZPFBEQAAFKNBKIDUJJDIOZYQWIXJI9ENJRDANLLLQVJA9PWUAWHXD
Therefore, it’s pretty clear that whoever made the transaction had access to your seed.
If it wasn’t you, it was most likely the creator of that generator website you’ve used.
I agree with you that a warning in the Lightwallet to not use any online generators could have probably prevented this from happening.
But I think the Foundation considers it common sense not to create a seed (or any „password“) on some website. Even more so after the January thefts had been discussed pretty much everywhere and they made a blogpost about how to properly create a seed: https://blog.iota.org/the-secret-to-security-is-secrecy-d32b5b7f25ef
The new Trinity wallet will have a built in seed generator to prevent these things. I know this won’t help you though.
You can track where your funds are going to be transferred to on thetangle.org, but it will become very difficult once they get split into smaller portions and distributed over several addresses (which is what usually happens to stolen coins sooner or later). Tracking your funds also won’t help you that much, I guess. Even if you know which address they are at, you’ll never know whose address it is.
Unfortunately, there’s nothing you can do now, except file a claim with your local (cybercrime) police and hope that the thief gets caught.
If this ever happens, you’ll have to provide proof that those stolen coins belong to you. Even if you don't want to involve the police, please make sure to keep your seed and all evidence of where your bought your coins from and where you sent them to afterwards (for example safe your trade history and your withdrawal history from your Bitfinex account or wherever you purchased your coins).
I'm very sorry that you've lost your funds!
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