IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Hardware & Software Remarks
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S 4.99 Protection against subsequent changes to
information
Initiation responsibility: Head of IT Section, IT Security Management
Implementation responsibility: Administrators, users
Files which are passed on to third parties can generally also be edited by those
third parties. This is not always in the interest of the creator of the files. A
form of protection against subsequent changes, the forwarding of extracts or
further processing would therefore be desirable.
A problem that is often encountered is that information is made available to
third parties via the Internet or other networks, but it may not be intended that
it should be printed out hundreds of times or integrated seamlessly into other
documents.
There are various solutions to this, which in some cases can also be combined
with each other. Examples here are:
- Using digital signatures in order to prevent changes from being made to
files without this being noticed (see also S 4.34 Using encryption,
checksums or digital signatures or S 3.23 Introduction to basic
cryptographic terms).
- Adding copyright notices to WWW information or files. These can be
formulated as follows: "This document and all of its parts is protected by
copyright. Any use of the document outside the constraints of the
Copyright Act without the approval of the author is inadmissible and
punishable." and "Copyright (©) 7/1999 by BSI".
- The use of file formats which make it more difficult to make subsequent
changes or edit extracts in any way. Postscript can be used for this, for
example, or the security properties of application programs, such as in the
case of PDF files.
PDF documents can be assigned access restrictions when they are created.
The opening, printing or copying of PDF files can be inhibited, for
example.
Two types of password can be assigned with Acrobat Exchange, i.e. the
application with which PDF files can be created and edited. One type of
password is required for opening the document, and the other for changing
the security attributes. PDF documents that are protected against
unauthorised opening are encrypted with RC4. The following functions can
be inhibited using the security attributes:
- Printing
- Modifying the document
- Selecting text or graphics
- Adding or changing notes and form fields
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IT-Baseline Protection Manual: Oktober 2000