Error: Failed account unlock attempt, is this an attack?

Question

If I use my

geth --identity "MyNodeName" --rpc --rpcport "8545" --rpccorsdomain "*" 
--datadir Users/xxxx/TestChain1 --port "30303" --rpcaddr 
"127.0.0.1"  --nodiscover --rpcapi "db,eth,net,web3,personal" -- 
networkid 123 init /Users/xxxx/CustomGenesis.json


 geth --identity "MyNodeName" --rpc --rpcport "8545" --rpccorsdomain 
 "*" --datadir Users/xxxx/TestChain1 --port "30303" --nodiscover -- 
 rpcapi "db,eth,net,web3,personal" --networkid 123 console

Everything works fine. But if I change rpcaddr "127.0.0.1" to a static address like 129.215.199.18 and run the above code, i will get the following warning in geth:

Failed account unlock attempt            
address=0x621C385fe616fBe096322E71d6f02631d520C1Ca 
err="could not decrypt key with given passphrase"

Note that this is the only account I had. Even if I try to unlock my account once I keep getting the above warning. It also prevents me to deploy the contract to the blockchain if I use remix and metamask. But I will not have any issue if I use rpcaddr "127.0.0.1" in the above command line.

Also, when I send only one transaction via geth, the console keeps saying that a transaction has been submitted.

Question: What is the problem?

Answer 1

This is a brute-force attack against your password. Besides potentially stealing all of your ETH, descryption is relatively expensive computationally and could be a DOS vector.

You should never expose the personal API to the open internet. Consider disallowing external connections by setting your rpcaddr and rpccorsdomain to localhost. Even better, use IPC instead of RPC if your connection is local.

Answer 2

Sure, this is brute-force attack trying to unlock an account and send out a transaction. Never never never open up rpc port in public.