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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><HTML><HEAD><TITLE>Security Issues</TITLE><METANAME="GENERATOR"CONTENT="Modular DocBook HTML Stylesheet Version 1.57"><LINKREL="HOME"TITLE="Advanced Bash-Scripting Guide"HREF="index.html"><LINKREL="UP"TITLE="Miscellany"HREF="miscellany.html"><LINKREL="PREVIOUS"TITLE="Assorted Tips"HREF="assortedtips.html"><LINKREL="NEXT"TITLE="Portability Issues"HREF="portabilityissues.html"><METAHTTP-EQUIV="Content-Style-Type"CONTENT="text/css"><LINKREL="stylesheet"HREF="common/kde-common.css"TYPE="text/css"><METAHTTP-EQUIV="Content-Type"CONTENT="text/html; charset=iso-8859-1"><METAHTTP-EQUIV="Content-Language"CONTENT="en"><LINKREL="stylesheet"HREF="common/kde-localised.css"TYPE="text/css"TITLE="KDE-English"><LINKREL="stylesheet"HREF="common/kde-default.css"TYPE="text/css"TITLE="KDE-Default"></HEAD><BODYCLASS="SECT1"BGCOLOR="#FFFFFF"TEXT="#000000"LINK="#AA0000"VLINK="#AA0055"ALINK="#AA0000"STYLE="font-family: sans-serif;"><DIVCLASS="NAVHEADER"><TABLEWIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><THCOLSPAN="3"ALIGN="center">Advanced Bash-Scripting Guide: An in-depth exploration of the art of shell scripting</TH></TR><TR><TDWIDTH="10%"ALIGN="left"VALIGN="bottom"><AHREF="assortedtips.html">Prev</A></TD><TDWIDTH="80%"ALIGN="center"VALIGN="bottom">Chapter 33. Miscellany</TD><TDWIDTH="10%"ALIGN="right"VALIGN="bottom"><AHREF="portabilityissues.html">Next</A></TD></TR></TABLE><HRALIGN="LEFT"WIDTH="100%"></DIV><DIVCLASS="SECT1"><H1CLASS="SECT1"><ANAME="SECURITYISSUES">33.8. Security Issues</A></H1><DIVCLASS="SECT2"><H2CLASS="SECT2"><ANAME="INFECTEDSCRIPTS">33.8.1. Infected Shell Scripts</A></H2><P>A brief warning about script security is appropriate.	  A shell script may contain a <ICLASS="EMPHASIS">worm</I>,	  <ICLASS="EMPHASIS">trojan</I>, or even a <ICLASS="EMPHASIS">virus</I>.	  For that reason, never run as root a script (or permit it	  to be inserted into the system startup scripts in <TTCLASS="FILENAME">/etc/rc.d</TT>) unless you have obtained	  said script from a trusted source or you have carefully analyzed	  it to make certain it does nothing harmful.</P><P>Various researchers at Bell Labs and other sites, including M.	  Douglas McIlroy, Tom Duff, and Fred Cohen have investigated the	  implications of shell script viruses. They conclude that it is	  all to easy for even a novice, a <SPANCLASS="QUOTE">"script kiddie"</SPAN>,	  to write one.	    <ANAME="AEN15781"HREF="#FTN.AEN15781">[1]</A>	  </P><P>Here is yet another reason to learn scripting. Being able to	  look at and understand scripts may protect your system from	  being hacked or damaged.</P></DIV><DIVCLASS="SECT2"><H2CLASS="SECT2"><ANAME="HIDINGSOURCE">33.8.2. Hiding Shell Script Source</A></H2><P>For security purposes, it may be necessary to render a script	  unreadable. If only there were a utility to create a stripped	  binary executable from a script. Francisco Rosales' <AHREF="http://www.datsi.fi.upm.es/~frosal/sources/"TARGET="_top">shc -	  generic shell script compiler</A> does exactly that.</P><P>Unfortunately, according to <AHREF="http://www.linuxjournal.com/article/8256"TARGET="_top">an article in	 the October, 2005 <ICLASS="EMPHASIS">Linux Journal</I></A>,	 the binary can, in at least some cases, be decrypted to recover	 the original script source. Still, this could be a useful	 method of keeping scripts secure from all but the most skilled	 hackers.</P></DIV></DIV><H3CLASS="FOOTNOTES">Notes</H3><TABLEBORDER="0"CLASS="FOOTNOTES"WIDTH="100%"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="5%"><ANAME="FTN.AEN15781"HREF="securityissues.html#AEN15781">[1]</A></TD><TDALIGN="LEFT"VALIGN="TOP"WIDTH="95%"><P>See Marius van Oers' article, <AHREF="http://www.virusbtn.com/magazine/archives/200204/malshell.xml"TARGET="_top">Unix	      Shell Scripting Malware</A>, and also the	      <ICLASS="EMPHASIS">Denning</I> reference in the <AHREF="biblio.html#BIBLIOREF">bibliography</A>.</P></TD></TR></TABLE><DIVCLASS="NAVFOOTER"><HRALIGN="LEFT"WIDTH="100%"><TABLEWIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top"><AHREF="assortedtips.html">Prev</A></TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="index.html">Home</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top"><AHREF="portabilityissues.html">Next</A></TD></TR><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top">Assorted Tips</TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="miscellany.html">Up</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top">Portability Issues</TD></TR></TABLE></DIV></BODY></HTML>
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