TrojanDownloader:SWF/Nerner.A is a trojan that, when executed, attempts to run a file detected as Worm:JS/Nerner.A from a certain Web site. The worm attempts to spread via renren.com, a social networking Web site.

Windows Defender detects and removes this threat.

This threat uses a Java vulnerability (CVE-2013-1493) to download and run files on your PC, including other malware.

It runs when you visit a hacked or malicious website and if you have a vulnerable version of Java.

The following versions of Java are vulnerable:

• Oracle Java JDK and JRE 7 Update 15 and earlier
• Oracle Java JDK and JRE 6 Update 41 and earlier
• Oracle Java JDK and JRE 5 Update 40 and earlier

To check if you're running a vulnerable version of Java:

1. In Control Panel, double-click Programs.
2. If Java is installed you will see it in the list of installed programs. Click it to open the Java Control Panel.
3. On the General tab, click About to see which version of Java you have installed.

You might get an alert about this threat even if you're not using a vulnerable version of Java. This is because we detect when a website tries to use the vulnerability, even if it isn't successful. This doesn't mean that you have been hacked; it means someone has tried to hack into your PC.

Find out ways that malware can get on your PC.

Win32/Wordjmp exploits a vulnerability found in Microsoft Word 2002 and Microsoft Word 2003 which could allow an attacker to remotely execute arbitrary code on impacted systems. Details on the vulnerability can be found in the Microsoft Security Advisory (919637) at http://www.microsoft.com/technet/security/advisory/919637.mspx.