IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Organisation Remarks
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3. Have all superfluous cgi programs and WWW pages been deleted?
4. Is the HTTP port (usually port 80) the only accessible port on the computer
(see S 4.97 One service per server)?
5. Is appropriate regular backing up of the stored data ensured (see Chapter
3.4 Data backup policy)?
6. If cgi programs are used, are these programmed sufficiently securely? It is
not permitted to accept any input values unchecked. It must be ensured that
buffer overflows and race conditions are ruled out. The taint check should
be activated in all Perl scripts.
7. Is there a functioning routine for a regular integrity check (e.g. Tripwire;
see S 4.93 Regular integrity checking)?
Example: Setting up a simple WWW server
On a WWW server of this type the contents of individual pages change only
rarely; no cgi programs are used and there is no particular access protection.
The individual WWW documents are loaded onto the WWW server via a data
medium. On a server like this, all system files and also all HTML pages can
be given write protection. Although an attacker is able to modify temporary
files and log entries in a setup of this kind, he cannot make any changes to the
system itself. Access protection in this form should be implemented by a
physically write-protected medium, for example one or more CD-ROMs or a
write-protected removable hard disk. At the very least, however, regular
integrity checks should be performed (see S 4.93).
Functionalities in the http daemon that are not required should be deactivated,
i.e. those such as the possibility of executing cgi scripts. Whatever the case,
cgi programs supplied with the system should be removed.
In one frequently encountered variant of a simple Web server, the documents
can be modified interactively on the WWW server with corresponding
authorisations. In this case, protection against unauthorised changes and a
regular integrity check at short intervals are especially important.
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IT-Baseline Protection Manual: Oktober 2000