Forum Moderators: goodroi
Protecting yourself comes down to securing your webserver.
The robots.txt file is just a file on your webserver - if security on your webserver is compromised, that file can be altered just as easily as any page.
Change passwords etc. If you feel it might be an inside job, I'd run a script keeping an eye on the date/time stamp of the robots.txt file (that in itself could be easily compromised though).
TJ