Realtor.com's website has been down since midday Tuesday (update: the site is back online), along with other Move services like Top Producer. In a statement, the company identified a Distributed Denial of Service (DDoS) attack as the reason for the outage.

The attack against Move's web properties is the latest in a string of recent DDoS attacks across the Internet. Ancestry.com was also down Wednesday. The World Cup website, along with RSS reader Feedly and Realtor-favorite Evernote were targets of DDoS attacks last week.

Attack of the Zombie Computers!

So what is a DDoS attack, anyway? It's a tactic that malicious hackers use to take down a website or network by overwhelming it with a high volume of traffic. Think of it as a mass stampede of thousands or millions of computers all trying to access a site at the same time.

It's called a Distributed Denial of Service attack because the intent is to deny legitimate users from accessing a website, therefore crippling a business for the duration of the attack. Banks, media, and other major sites are frequent targets of DDoS takedowns.

Hackers use something called a "botnet" to execute DDoS attacks. A botnet is a network of linked computers that are used collectively to pummel a target's server. These computers often belong to regular home or business users, but have been infected by a virus or malware. Once infected, hackers can control these computers remotely and use them to attack a website.

Should I Be Worried?

While there's been a huge spike recently in the frequency and severity of the attacks, agents shouldn't worry about their sites being a target. DDoS attacks mostly target huge sites and online services only. It's very unlikely anyone will be coming after your agent site.

However, if you want reassurance on the safety of your site, contact your website provider and ask what plans they have in place to counter a DDoS attack. A reputable company will be happy to answer your concerns. If you're a DIYer with a WordPress or other similar platform, always make sure your website is running the latest version of your website or blogging program. Keeping your site's backend updated makes it more difficult for hackers to compromise it and use it to attack other sites during a DDoS.

If an attack strikes a service you use, look to company communications to see if your data has been compromised. DDoS attacks are sometimes used as a smokescreen for hackers whose real motive is to steal sensitive data like credit card numbers. In most cases, your data usually remains safe. Move, for example, has assured users that their data has not been compromised.

Here's advice you can use now to protect yourself: Change your passwords frequently, and make sure they're tough to figure out. For tips on creating better passwords, read this article. Make sure your computer is free of malware and viruses, and that you have an updated anti-virus program installed. AVG and Malwarebytes are two free programs that I highly recommend.

Remember, eternal vigilance is the price of not being sucked into a zombie computer network. Frequent backups and virus scans (not to mention a little common sense) should keep you and your computer out of harm's way.