wtf? i woke up and it says my bitcoin got sent to some one's address

[Abdussamad]

if i have an offline wallet, how do i see how much bitcoins is in my wallet?  (serious questions)
i usually just have it up on my screen minimized and i check it every now and then.

You can install a watch only wallet. You will need a deterministic wallet like Electrum or Armory or the upcoming multibit hd.

[Abdussamad]

that would be my guess as well but if my wallet was not shared publicy, they would still need both my dropbox username and corresponding pw to obtain access to my wallet.

Maybe they phished you. Maybe someone at drop box stole your wallet. Remember you have no idea who stole your coins. There is just this address you see. Anyone in the world who had access to the file could have stolen it. Cloud backups are supposed to be spread around multiple servers in multiple data centers all in the name of redundancy. How can you secure money in such a system?

[BeepBeep2]

yea im running windows but how does that even happen.  im 99.9% sure i dont have a key logger.  i work in IT and im not that dumb to get a virus and stuff that easily.  they would need to have my my wallet in order to send themselves bitcoin right?  it is password protected.  im using multi-bit

If you are a miner, save, and make multiple backups of a wallet to keep in cold storage.
Go ahead and have the network send bitcoins to this wallet, but don't actually have the wallet open.

When you need to access the money in the wallet, to be most secure, copy the wallet on a safe computer to make whatever transactions you need out of it.
Immediately afterwards, delete all files from the computer, but keep wallet backups.

[Sonny]

Cloud backups are supposed to be spread around multiple servers in multiple data centers all in the name of redundancy. How can you secure money in such a system?

People can encrypt the wallet file using truecrypt or archive softwares with a good password, before putting it on dropbox.

[toknormal]

Hauwd-the-noo people.

Can we get back to the OP's post for a moment. We don't even know what wallet they were using or whether it was encrypted or not.

Could the OP please provide some details about that ? e.g. was it QT with a password encryption ?

How did you check the balance - using the blockchain or the wallet ? Did you definitely check the blockchain? Are you sure you didn't make a payment or something and your wallet sent the change to change addresses ? In that case the blockchain would show your original address as empty but your wallet would still have access to the change addresses.

If your wallet wasn't encrypted then it may simply have been 'stone' by a virus. What software have you downloaded that may have piggy-bagged a trojan ? Are you on Windows ?

I'd be interested to know more about this.

[film2240]

its on my computer

Let me guess, you are running Windows. 

Never use Windows to store your wallets.

This is bullshit. Using windows, never had any wallets stolen. Stupid people will install malicious software no matter which os they use. From what I see most of bitcoin stealing stuff comes with bitcoin related software, a different os will not protect you from that.

Majority of the people who got their wallet stolen uses Windows. That is a fact.

Are mac users like myself less likely to have this issue?Or should I just be vigilant as everyone else needs to be?What solutions exist for an offline wallet?As I'm looking into one due to recent unusual access attempts to my online wallet (it's safe as I have 2 factor login).My coins are still safe/there it's just more important now to get them moved to an offline wallet though.

[prezbo]

Are mac users like myself less likely to have this issue?Or should I just be vigilant as everyone else needs to be?What solutions exist for an offline wallet?As I'm looking into one due to recent unusual access attempts to my online wallet (it's safe as I have 2 factor login).My coins are still safe/there it's just more important now to get them moved to an offline wallet though.

Don't install any suspicious bitcoin-related software and you'll be fine on any os, or if you really have to, install it on another computer.

[Gator-hex]

if i have an offline wallet, how do i see how much bitcoins is in my wallet?  (serious questions)
i usually just have it up on my screen minimized and i check it every now and then.

You can install a watch only wallet. You will need a deterministic wallet like Electrum or Armory or the upcoming multibit hd.

Just use www.blockchain.info to watch your Bitcoin wallet, for Litecoin I use http://explorer.litecoin.net
My real wallet is on an encrypted Ubuntu home partition. I only log into when I want to buy something.

Install altcoin clients on different encrypted home partitions. Never run a miner and your wallet in the same place. Never trust a 3rd party to hold your Bitcoins! 

[fluidjax]

I'm sorry for the OP's loss.

I would say if you have more than 5 Bitcoins, buy a cheap laptop (second hand if you like) and dedicate it to storing your Bitcoins, and nothing else.
You can use Armory for signing your transactions with an offline computer that never touches the internet.
Every online Bitcoin service should be using 2FA, if they don't have that facility, then don't use them.

Holding 5 bitcoins, your cheap laptop is only going to be 10% of your Bitcoin worth, and you will be almost guaranteed security (unless someone breaks into your house whilst you have your wallet unlocked).

Until something like Trezor comes along people need to take serious precautions.
I wouldn't walk around with the equivalent of 10bitcoins in the leather wallet in my back pocket, and people shouldn't put Bitcoins in a internet connected computer that you do lots of other things on.

Come on people,  it may be virtual money, but its not virtual pain when you lose it. 100's of people on this forum can help you with securing your Bitcoins, pull you finger out and do it properly.

[Amphytrion]

Mind telling us the versions of Multibit, Windows and Java?

I ask because the original bitcoin client seeds the random number generator "with a screen scrape and other hardware sources", specifically when it's running on Windows.

Whereas bitcoinj (which Multibit relies on) simply calls SecureRandom() without seeding the PRNG first.

[R0yalAir]

its on my computer

Let me guess, you are running Windows. 

Never use Windows to store your wallets.

And never use Linux to store your wallets ?
Too big.
Give us an alternative.

[nanobtc]

yea im running windows but how does that even happen.  im 99.9% sure i dont have a key logger.  i work in IT and im not that dumb to get a virus and stuff that easily.  they would need to have my my wallet in order to send themselves bitcoin right?  it is password protected.  im using multi-bit

You don't have to be dumb to get a virus and stuff, you just have to be running an insecure version of Windows. Some versions can have a running VNC server injected into memory, the attacker can log on to it as SYSTEM, and you are pwned without ever clicking on a link, or getting a funny email. Some tools let you remotely add a user.