What is a double spend?

[BigO2222]

I woke up this morning to three transactions of sent bitcoins in a 2 minute period that I did not make.  After initial panic, I realized that if it were caused by being hacked, they wouldn't have taken such a small percentage of the wallet balance and wouldn't have done it in three separate transactions.  So, can someone tell me what happened and is there any way to get the bitcoin back?


Thanks

[centurionMiner]

Be more specific please:

Is a software wallet or online wallet?

Is a very strange issues. No one can use your wallet if they haven't your wallet.dat or your seed (electrum)

[BigO2222]

I guess I'm not sure.  I use a blockchain wallet for my transactions, sometimes from my phone and sometimes from desktop.

https://blockchain.info/tx/fe2c0fffdc7fad33028f2c533ac34e9ac2abae0c52d0a266202cf62e251c8f16

https://blockchain.info/tx/501b23f53ae54436fd0293407967ca5687509236937e6b7699e91baf793916f6

https://blockchain.info/tx/ab8c2b9dd39e7a7a1e6da16504222fa543f1dffe4ad25df594e2cb439e552800

These are the three transactions.  Does this help?


Thanks again

[BigO2222]

When I saw the three transactions this morning I sent the remaining balance from that wallet to a different wallet.  This was 5.5 hours after the initial three transactions however.  Is that what you're seeing in reference to me having zero bitcoin?

My other wallets seem to be fine.

[achow101]

Did you, at some several days or weeks ago, attempt to make three transactions that have the same values sent as these three transactions? If you did, did those three transactions not confirm and eventually the balance went back to you and it looked like the transactions had been "returned"? If so, what happened then was that a miner still had your transactions and eventually included them into a block.

You should also stop using blockchain.info's wallet as it is well known that their wallet is poorly written (especially the fee estimation and coin selection stuff) and has had security issues in the past.

[BigO2222]

Ok, that is very helpful thanks.  That is a very reasonable possibility as to what happened.  Is there a way I can confirm that by looking at my previous transaction history?

As a bitcoin newbie I thought blockchain.info's wallet was one of the safest choices.  What are better options?

[FlamingFingers]

Ok, that is very helpful thanks.  That is a very reasonable possibility as to what happened.  Is there a way I can confirm that by looking at my previous transaction history?

As a bitcoin newbie I thought blockchain.info's wallet was one of the safest choices.  What are better options?

Electrum would be a good choice. There is also Bitcoin Core wallet (but if you don't mind downloading 110-ish GBs of data, and you may encounter a few issues as well). Don't worry, I thought that at first, too, until I encountered the fees issues.

Looking at your transactions, did you make those transactions yourself anytime before? If you did, can you recall where you send them to? Although I know Blockchain.info wallet can make some weird transactions for old addresses sometimes, it doesn't make transaction on its own.

[achow101]

Ok, that is very helpful thanks.  That is a very reasonable possibility as to what happened.  Is there a way I can confirm that by looking at my previous transaction history?

Unfortunately no. You will just have to try to remember if you made any transactions in the past few days.

As a bitcoin newbie I thought blockchain.info's wallet was one of the safest choices.  What are better options?

Blockchain.info's wallet is one of the worst wallet choices available. You should use any wallet listed here: https://bitcoin.org/en/choose-your-wallet. All wallets listed there are vetted before being listed. Notice how blockchain.info is not listed. Read the descriptions provided and the descriptions of the ratings for the various security and privacy aspects of each wallet.

I recommend that you use Electrum.

There is also Bitcoin Core wallet (but if you don't mind downloading 60-ish GBs of data, and you may encounter a few issues as well).

The blockchain is actually at ~110 GB right now. However pruning can be enabled to save space on the hard drive. Pruning will not effect the time it takes to download and verify the blockchain though as the whole thing will still need to be downloaded and verified (i.e. bandwidth is consumed, but not disk space).

[FlamingFingers]

There is also Bitcoin Core wallet (but if you don't mind downloading 60-ish GBs of data, and you may encounter a few issues as well).

The blockchain is actually at ~110 GB right now. However pruning can be enabled to save space on the hard drive. Pruning will not effect the time it takes to download and verify the blockchain though as the whole thing will still need to be downloaded and verified (i.e. bandwidth is consumed, but not disk space).

LOL. Well, I haven't checked it since I got involved into the Bitcoin world earlier (I have a bad network as well so that adds up...). Thanks for pointing it out (I have edited my post).

[BigO2222]

I make quite a large amount of transactions every week that are those sizes.  They are generally sent to one of two different recipients.  It seems reasonable that they are transactions I sent previously.

If I send the transaction data to the most likely recipient they should be able to confirm whether or not they were they received those particular transactions correct?

I will change to Electrum and truly appreciate the expertise and knowledge.  It is very disconcerting to be uneducated and feel nervous about the security of life changing amounts of bitcoin.

[achow101]

If I send the transaction data to the most likely recipient they should be able to confirm whether or not they were they received those particular transactions correct?

Yes. Contact whoever you think received the Bitcoin and ask them if those transactions are in their wallet.