What can a hacker do with just one password?

Q. I received a letter from a site I use. It says that someone broke into their servers and stole passwords. Could a hacker use that password to guess my other passwords?

A. It’s possible. It depends on whether the password was hashed. This means the company replaced the password with a bunch of gibberish in their database.

If the company “salted” the hash, it would be even tougher for the hacker to get. From there, it depends on how simple your password was. If you didn’t use a complex password, the hacker might try to dig up more of your accounts, since you’re an easy target.

Test your password’s strength on How Secure is My Password, https://howsecureismypassword.net/. If it thinks your password is weak, you need to make it stronger now!

Find free classes online

Q. School’s out for summer, but I still want to keep a leg up on my studies. Do you have any online tools I can use?

A. There are dozens of great tools online. CourseRA, https://www.coursera.org, and Udacity, https://www.udacity.com, both round up free online courses from top universities such as Brown, Harvard and Yale. Some of them require traditional enrollment but most just give you the resources and let you learn at your pace.

You might even be able to get credit for some of them. If you don’t find anything you like there, check out The Khan Academy, https://www.khanacademy.org/, and Academic Earth, http://academicearth.org/. These tutoring sites will help keep your mind fresh. They’ll even tutor you on practical knowledge and current events.

The best time to replace your computer

Q. My computer is about two years old and it’s starting to slow down in a big way. Do you think it’s time to replace it?

A. It depends on how you’ve used the computer. Most computers have a lifespan of three years or more. If your computer is a desktop, you should be able get at least four years out of it.

In your case, try to do some maintenance fixes before you junk the computer for a new one. Clean up your startup with Autoruns, http://technet.microsoft.com/en-us/sysinternals/bb963902.aspx; defragment with Defraggler, www.piriform.com/defraggler; run a virus scan; and clean out clutter with a program like CCleaner, www.piriform.com/ccleaner.

If those don’t bring back some of its old speed, think about hardware upgrades, since the problem is probably an aging part.

Real ways to make money online

Q. I’m looking for some real ways to make money online. Do you have any ideas?

A. Have you ever heard of Amazon’s Mechanical Turk service, https://www.mturk.com/mturk/? It lets you complete odd online jobs for cash.

These can be anything from finding a contact email on a website to writing an in-depth how-to article. You won’t be rolling in the dough, but if you spend enough time on the site, you can make some real cash.

To sign up, you need to be an Amazon member. Amazon will review your profile, which will take up to 48 hours. After that, you’re free to take as many jobs as you can handle.

Protect your PC from prying eyes

Q. My sons have a bad habit of rifling through my computer and reading things they shouldn’t. How can I stop them from doing that?

A. You should start by having a chat with them about privacy. Tell them that it’s not OK to snoop through another person’s files.

Of course, kids will be kids and a talk probably won’t cure the problem entirely. In that case, use a program like Lockscreen Pro, http://download.cnet.com/Lockscreen-Pro/3000-2084_4-75833346.html. It goes above and beyond the default lockscreen in Windows. It has a battery meter for laptops, screen dimming and more.

It can even take a snapshot of anyone who tries to use your computer when it’s active. That way, you’ll be able to catch those snooping sons of yours in the act.

Kim Komando hosts the nation’s largest talk radio show about consumer electronics, computers and the Internet. Hear it locally at 94.3 WSC News Radio noon-3 p.m. Sundays. For more information, go to www.komando.com.