Introduction
Secure rm (remove on unix) is a simple tool which, before actually
removing a file, overwite it's content with some random data. It does
this in several steps:
- Identify the actual size of the file
- Calculate the amount of 512-byte-blocks needed to overwrite this
file. So a file of 800 bytes, needs 2 blocks of 512 bytes to overwrite
the entire content of the file. Why 512 bytes would you ask? Very good
question: the smallest amount of data a harddrive can read or write is
512 bytes, a hardware-sector on disk. This is why srm use
512-byte-blocks.
- Open the file for writing and make sure to start at the very
beginning of the file.
- Write the correct amount of random data. This random data (512
bytes) is gathered at startup and written as much as needed to
overwrite the file.
- Close the file and remove it. What remains of this file, from a
forensic view, is a file containing garbage.
What's New
July 2, 2006.
Initial version, 0.2
Usage
The usage is very simple:
srm <filename> [filename] [filename] [...]
srm doesn't have recursive options, nor it can delete
directory-entries. Only plain files.
Download
SRM version 0.2 can be downloaded:
srm
version 0.2
Copyright
SRM
is
released under the GPL.
Warning
Be aware that just overwriting data once is not a garantee for
beiing totaly secure ( See
http://www.porcupine.org/forensics/forensic-discovery/
for a detailed
explaination on this theory). I have not tested this against highly
fragmented filesystems to be very sure every fragment is overwritten.
Why not? I don't have that kind of filesystems here. So if you can test
it for me, i would be very happy if you could send me some results.