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It depend on how the account is compromised.

There are 5 main keys to access different level of the account.
1 - Posting Key
2 - Active Key
3 - Owner Key
4 - Memo Key

5 - Master Password

If your private posting key is accessed - it can only effect your voting power
If your active key is accessed - it can be used to withdraw your STEEM and SBD balance, can also power down and take your SP vests, but it will take 7 days for 1st power down.
If owner key is accessed - they can change all other keys
Memo key is least defective - only messages can be unencryted

But be careful with the master pass. If you lose it you lose the account.

To prevent any intrusion use the key only when necessary i.e. use only the posting key for posting, upvoting and commenting; use active key only when you need to make a transaction or wallet balance related work. Never use the owner key or master pass.