how can I possibly prevent fraudulent use of my personal info?
Apply to all three of the credit bureaus to put a security freeze on your credit report (not a fraud alert, they are two different things-- the latter is temporary). It will cost you $10 or so for each one and be painfully inconvenient when you need to do anything involving credit (applying for job, buying a cell phone, etc.).
Keep an eye on Credit Karma. Be mindful of inquiries you didn't initiate; it's an indication someone is hammering your credit for new lines.
Dispute anything fraudulent as soon as it shows up, before the thief has an opportunity to max out your accounts and bust out. Not that the stolen money is your problem, but the banks and credit bureaus will certainly act like it. Mitigate this damage.
Alternately you can sign up for one of the credit monitoring rackets to protect you against the very threat they created.
What are the hackers likely to target?
As to what they'll target, it's all the same stuff they always have:
- Tax returns. File early, before fraudsters do.
- Employment records, including modification of direct deposit accounts.
- Health savings accounts.
- Existing credit lines. Your card issuers will likely be sending out new cards in the next few weeks, but you can pre-empt this and claim all your cards were stolen and have them re-numbered.
- Opening new lines of credit. Everything from credit cards to HELOCs. They have everything they need to impersonate you.
If you have money stored anywhere other than your mattress, assume it's open for the taking unless it's secured by credible 2FA.