FTP Trojan is one of the spyware which may run in user desktop PC background and capture FTP credentials (username/password).
If your website is unforunately modified, you need to do the following in sequence –
- Reset your DirectAdmin, FTP password
- Scan your desktop PC/notebook for any virus/spyware/Trojan
- Delete the current web page, and re-upload it.
Other Related Information –
http://en.wikipedia.org/wiki/Gumblar
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Below is one of the example trojan –