Gumblar appears to be a combination of exploit scripts and malware. The scripts are embedded in .html, .js and .php files using obfuscated Javascript. They load malware content from Third Party sites without the user’s knowledge, while also stealing FTP credentials from the victim’s computer, which then allows it to spread and infect additional sites. Therefore, when someone visits such an infected site they get infected; if they have FTP credentials for a website on their machine then those sites get infected too. This explains the exponential growth of the exploit in such a short space of time.