Whether you were hacked, phished, had malware installed or just don’t know what the heck happened but there’s somebody all up in your e-mail, here are a few good first steps to take following an incident. This is by no means comprehensive, but it’s a good start.

Ask Yourself Why

While you are fixing things, it’s a good time to take a step back, and ask yourself a more basic question: What was the reason for the breach? If it was your bank account, the answer may be obvious. In other cases, such as e-mail, it can be for a host of reasons — from using it to send spam, to requesting money from your contacts, to getting password resets on other services. An attacker may even be trying to gain access to your business. Knowing why you were targeted can also sometimes help you understand how you were breached.

Reset Your Passwords

Immediately change the password on the affected service, and any others that use the same or similar password. And, really, don’t reuse passwords. You should be changing your passwords periodically anyway as a part of routine maintenance. But if you’ve just been hacked, it’s now more urgent. This is especially true if you reuse passwords or use schemes that result in similar passwords
(like 123Facebook, 123Linkedin, 123Google).

It’s very common for people to use similar or the same password but it’s very rare for people to realize that it creates a liability for them to do it and that they need to change their password after they’ve been hacked.

Go through and change the passwords to your most sensitive accounts (banking, email, investment) as well as to the one that was hacked (if possible). Make sure your new password is even better than your last and. If for some reason changing the password is not possible, you need to call the company and freeze the account.

Update and Scan

Almost all malware is installed by victims themselves, if unknowingly. And if something nasty is on your computer, you need to get it off before you start a recovery process. Make sure you are running the most recent version of your operating system. Download a solid anti-virus product and run a scan for malware and viruses that may have been the source of the attack. This is the most basic thing you can do, so do it now. And moreover, use a brand-name commercial program that you pay for.

Malware antivirus software isn’t fool proof, but it’s better than nothing. It is advisable to not download free antivirus software. Often those are Malware themselves.

Take Back Your Account

Most of the major online services have tools in place to help you get your account back after it has been taken over by someone else. Typically, you’re going to need to be able to answer some questions about your account. Typically, you can find your way back in by searching for its name plus “account recovery.”

Check for Backdoors

Smart hackers won’t just get into your account, they’ll also set up tools to make sure they can get back in once you’ve gotten them out. Once you have your accounts back, you should immediately make sure there isn’t a back door somewhere designed to let an attacker back in. Check your e-mail rules and filters to make sure nothing is getting forwarded to another account without your knowledge. See if the answers to your security questions were changed, or if those questions themselves have changed.

Follow the Money

If there is an element of commerce involved in the affected account, thoroughly review any activity on that account. Verify that no new shipping addresses have been set up on your account, no new payment methods have been added, or new accounts linked. This is especially true of sites that let you make one-click purchases, or issue payment cards.

What criminals will often want to do is hook up a debit card to your account. If they add an address and then request a financial instrument, that is a way for them to monetize.”

Perform a Security Audit on All Your Affected Accounts

Often, one account is simply used as a gateway to another. Your Dropbox account may only be a means to get at something stored there. Your e-mail might only be a path to your online banking. Not only do you need to secure the account you know was hacked, but you need to check all the others it touches as well. Reset your passwords on those services and treat them as if they have been compromised.

De-Authorize All Those Apps

This is one of those non-obvious but important steps. One of the first things you should probably do if you’ve had an account compromise is de-authorize all the associated apps that use that account for login or for its social graph. For example, Google, Twitter, Facebook, Dropbox and many others support OAuth, which enables third party apps to use account APIs without having to give them the account login information. But if a hacker has used it to authorize another device or service, and remains logged in there, simply changing your password won’t get them out. There could be a rogue client out there that you remain unaware of even after regaining access to your account. The best bet is to pull the plug on everything you’ve given access to. It may be a pain to go back through and re-authorize them, but it’s less so than leaving a malicious individual lurking in your account. And in any case, doing so periodically is just good practice.

Lock Down Your Credit

It’s bad enough you had your email hacked, but you really don’t want your identity stolen as a result. Services like LifeLock will do this for you for a fee, but you can also do it yourself by contacting the three major credit reporting agencies directly. Depending on the state you live in, locking down your credit might be free, provided you’ve filed a police report.

Speak Out

“Say that your Facebook account gets hacked,” says Jakobsson, “there’s a good chance you won’t lose any money, but your friends might.” The mugged-in-London scam works by hijacking your identity to contact friends to request money. It’s also true, though less commonly so, on AIM and Google Talk and other services. There may also be data that you need to let others know has been accessed–from financial matters to sensitive personal information.

But there’s another reason to do this too which is to raise awareness. The best tactic of all is to do everything in your power to not be hacked: to run up to date software, use good password practices, and make backups of everything in your system.

https://www.wired.com/2013/03/what-to-do-after-youve-been-hacked/