Oracle has issued an emergency patch for its Java software after the U.S. government warned that PC users were at high risk for an attack.

Java is a popular computer programming language for writing Web applications and it is installed on hundreds of millions of computers worldwide, usually as part of a browser. Windows, Macs and Linux PCs all use Java and are vulnerable.

The attack was found in the latest version of Java, Java 7. It's unclear whether or not older versions of Java are at risk.

PCs become infected when they visit a website that has malicious code. Attackers are then able to control the PCs, which makes this hack especially dangerous.

Today Oracle, which owns Java, issued new software that fixes the problem but it's still important to protect your PCs.

First, check and see if you have Java software on your computer. If you do, you could be at risk. Update it or disconnect it from your browser. Here are some step-by-step guides to follow:

For a good explanation on what the security hole is and why everyone is freaking out, check out this post by security blogger, Brian Krebs, "What You Need to Know About the Java Exploit."

Don't miss: The 15 Most Important Security Startups Of 2013