Some of the worst adware, spyware and premium rate dialers are listed below.  You should protect your pc or mac from such software.

Spyware in the purest sense of the word is not a dangerous thing, designed only to display targeted advertising to you while browsing the internet. It was originally developed by marketers to be non intrusive and use very little system resources. You can easily recognize spyware by the display of pop up advertisements on your computer screen, often appearing when you perform searches or land on different websites.
Spyware can be very annoying, and in the past few years much of spy ware’s functional characteristics have begun to resemble spyware. A large percentage of spyware today includes code that tells the advertiser something about you. It often relays information about which sites you visit on the internet, how much time you spend on each site, and what type of content you viewed. Although marketing people consider this information to be harmless to you, most users consider this type of data gathering to be an invasion of privacy. Spyware that is delivered in the form of email often tells marketers when you opened the mail, how long you looked at it, and what you did with it.

Spyware is similar to spyware, but much more dangerous. Instead of transmitting information about your web behaviour to marketers, spyware is designed to steal confidential information such as account numbers, names, addresses, etc... As spyware continues to evolve into a more sophisticated marketing tool, much of it is now capable of gathering "non-marketing" information that is more sensitive in nature. This new type of hybrid spyware is sometimes referred to as "spyware-spyware".

Spyware is normally included in downloaded software known as "freeware". In exchange for using free software, you agree to the installation of spyware. Most free software includes a statement about the included spyware in a license agreement that usually goes unread. Other spyware comes in the form of email, with code hidden in embedded graphics or even in the HTML code. If you forward an spyware email to someone, they can get it too. Like spyware, spyware installs very quickly, often without the users knowledge. Spyware is not a virus, so antivirus software will never detect it.

If your computer is suddenly running very slowly, is plagued with pop-up ads, or if your browser home page has changed, chances are you have spyware on your computer. If you have spyware you probably have spyware too, as they both tend to go hand in hand.

Spyware and spyware can sometimes be difficult to remove, and it's best to use spyware removal software. Because the two are so closely related, most good spyware removers will find and kill spyware too. Since new spyware and spyware is introduced into the internet every day, you may have to try several spyware removers before you find one that will detect and destroy all the spyware on your computer. Many free spyware removers are available, but it's best to get a paid version of this software that will protect you from future problems.

Due to the danger and prevalence of spyware and spyware on the internet today, it is now considered a standard practice to use anti-spyware/anti-spyware software. For the best anti-spyware software, consider McAfee Anti Spyware, Spyware Doctor, Sunbelt Counter Spy, Ad aware, Web root Spy Sweeper, or e Trust Pest Patrol.

P2P Networking
PacerD
Padodor.w
PageRevisor
Painter
PAL Keylogger Pro
PAL PC Spy
Pandex
Pango
Paq Keylog
Parental Control Suite
ParisVoyeur
Payload:Messenger
PC ACME
PC Activity Monitor
PC Activity Monitor Net
PC Bloodhound Professional
PC Parent
PC Spy
PC-Parent
PECarlin
Peer
Peper
Perfect Keylogger
PerfectCleaner
PerfectNav
Permedia Ads
Pero.CN
Personal Antispy
Personal Web
PersonalMoneyTree
Pest
Pest 1.0
Pest Trap
PestBot
PestCapture
Phage Ports
Phase
PhazeBar
Phoenician Casino
Phoenix
Pib Toolbar
Pickoftheweb
PigSearch
Pinch
PKZ300b
PLook
PluginAccess
Poly-DL
Popper-Jhertz
Popup Network
PopUpDefence
Popuppers
PopUpWithCast
Popwin
Porn385
Porndialer.a
PornMagPass
PornoPlayer
Portal of Doom
PortalOfDoom
Power Key Logger
PowerReg Scheduler
PowerScan
PowerStrip
Powwabar
Praize
Prayer
Precision Time
PrecisionPop
PremiumConnectLoad
PreviewAdService
Privacy Defender
PrizeSurfer
Probol
Probot
Process Logger
Proclaim Dialers
ProfitZone
Progetto
PromulGate
ProRat
ProSiteFinder
Protected Storage Passview
ProvenTactics
Proxify
Proxxed.org
Proxy based anonymizers
Proxy-Agent.xI
Proxy-TSOH
Proxy.Win32.Agent.ei
Proxy7
ProxyBuster Browser
ProxyDex
Proxymod.com
Proxymouse
ProxyTopList
Proxytopsite
Proxyweb
Prutect
PRW
PSGuard
PSHope
PSW.Gamania
Ptakks
PurePrivacy
Purityscan
Push Toolbar
Pvsec
PWD Trojan
PWS-AHO
PWS-Banco.A
PWS-Banco.B
PWS-Ga.Rob
PWS-Maran
PWS-Steal.Klaipeda
PWS.BR.Banco
PWS.OLGame
PWSLegMir
PWSteal.Trojan
Q Nyx
Qdialer
Qidion
QQPass
QQRob
Qsearch
QucktIme.dialer
Quick Keylogger
QuickLinks
Quickmetasearch
QuickSearch Search Bar
Qukart-W
Rabio
Radar Spy
RadMin
Ramdud
RapidBlaster
RASDial-E
Rat
Raven
Ravupter
RaxSearch
Rays.A
RBlast.dldr
Rbot-JE
Rbot.gen
RCPrograms
RCSync
Real Spy 1.49
Real Spy Monitor
Realphx
Realtime-Spy
RedHand
RedHotNetworks
RedShell
RedV
RedZip
RegFreeze
RegiFast
RelatedLinks
Remote Control Pc 2000
Remote Desktop
Remote Havoc 2
remote password stealer
RemoteAnything
RemoteHack
Renek
Respondmiter
Revenger
Reverb 1.4
Reverse Trojan
ReWind
Reyds.A
RHEI
RieMon
Rinbot
Ring0 vxd keylogger
RipperPro
RK-70164
Ro2cn
Roach
RogueDrop
Roimoi
Rontokbro
Roogoo
Rootkit.Win32.WinIk
Rosibo
RoxRat
RSC
rSkype
Rtb666
RTK.D
Rugo
Ruledor.c
Rustock
RVP
RXToolbar
S-Redirect
Sa
Sabil
Sabotage
SafeguardProtect
Safenet
SafeSearch
SafeSurfing
Safety Browser
Sandboxer
Sandesa
Sasser Worm
Satan's Trick 1.0
Satans Back Door
Satray
Save Keys
SavingsHound
SC-Keylog
Scam.IWIN
SCBar
SCData Dialer
SchoolBus Trojan
SCN Toolbar
Scom Dialer
ScreenScenes
Screw-Bot
SdBot.gen
Se-sui
Search Assistant
Search Helping Wizard
Search Miracle
Search Relevancy
Search Toolbar
Search-Exe
Search123
Search3 Hijacker
Search4top
SearchAndBrowse
SearchAndClick
SearchBarCash
SearchBoss Toolbar
SearchCentrix
SearchClickAds
Searchex
SearchExplorer
SearchFast
Searchforfree
Searchforit
SearchingAll
SearchInWeb
SearchitBar
SearchLocate
Searchmaid
SearchMeUp
SearchNugget Toolbar
SearchPounder
SearchScout
SearchSeekFind
SearchSprint
SearchSquire
SearchTool
SearchWords
Searchwww
Secefa
SecondPower
SecureServicePack
Security Toolbar
Seek99
Seeker
Seekmo
SeekSeek
SeeqToolbar
SentryCam
SexFiles
Sexnow
SexoBFAX Dialer
SexoDial
Sexxxpassport
SexyBills
SexyVideoScreenSaver
Shadowbrowser
ShareAll v1.1
Shellbot
ShitHeep
ShopAtHomeSelect
ShopNav
Shopperreports
Shorty
Show Bar
Showbehind
ShowPass 1.0
SideBySideSearch
Sidefind
Sidesearch
Silencer
Silent Logger
Silent Spy
SilentSpy
SimilarSingles
Sinav
SinCity
SingWorm
SinRed Killer 0.1
SiteBar
SiteHistory
Sixem.A
SKL !.0
Skydance 3.6
SkyMaster
SkypeDefender
Slagent
Slammer worm
Slotchbar
Small-RN
Small.DAM
Small.DXM
SmallFun
Smart Finder
Smart Shopper
SmartAdware
Smartallyes
SmartBrowser
SmartDove
Smartpopups
Smiley Source
Smitfraud
SmsDialer
SmutFraud
Snape
Snapshot Spy
Snid
SniperNet
SoduiSearch
SoftEther
Softtec Dialer
Sogou
Sohanad
Solid Peer
Solitaire
SongSpy
SOSO Toolbar
SP2Update
SpamBlockerUtility
Spambot.BXB
Spamforo
Spammit
SpamThru
Spazbox
SpecialOffers
Specrem
Spector
Spector.Trojan
SpediaBar
Speer
SPlanet
Sporkeh
SpotOn
Spy Guardian Pro
Spy Keylogger
Spy Mail
Spy Wiper
Spy-Agent.ak
Spy-Agent.bg
Spy-Keylogger
Spy-Shield
Spy-Shredder
Spy.Win32.Agent.mn
SpyAgent
SpyAnytime PC Spy
SpyAnywhere
spyAOL
SpyAssault
SpyAway
Spyaxe
Spyblast
SpyBot-CY
Spybouncer
SpyBuddy
SpyCapture
SpyCar
SpyContra
Spycrush
SpyDawn
SpyFalcon
SpyGraphica Professional
SpyHeal
SpyMarshal
SpyMon
SpyOnThis
SpyPartner
SpyShredder
SpySoldier
SpySpotter
Spytech Spy Suite
SpyVampire
Spyware Cleaner
Spyware Quake
SpyWare Secure
Spyware Soft Stop
Spyware-Wiper
SpywareLocked
SpywareNo!
SpywareSheriff
Spywarestrike
SQuery
Srv.SSA-KeyLogger
SSK-UPdater
SSKC
ssppyy
SSpro
Starcross
StarDialer
StarHider Loader
StarLogger
STARR
StartGuard
Startmake
Startnow
StartPage
StartPage-HG
Startpage.16.BD
StartSurfing
Starware Toolbar
StatBlaster
Stawin-PWS
Stdecodw
Stealth Activity Reporter
Stealth Keyboard Interceptor
Stealth Redirector
Stealth Web Page Recorder
StealthWatcher 2000
Steganos Internet Anonym
StickyPops
Stop Popup Ads Now
Storm 1.2
Storm.Trojan
STRAd32
StripPlayer
Stwoyle
Sub Seven
SubSearch
SubSeven 2.2
Suggestor
Sumtax
Supaseek
Super Spider
Super Stealth Key Capturer:
SuperBar
Superlogy
SuperUtilBar
SupremeSpy
SuprIce
Surebar
Surf Accuracy
Surf Anonymous
Surf Player
Surf Speak
Surf Spy
Surfairy
SurferBar
SurfSideKick
Surila.aw
SweetBar
SwimSuitNetwork
Switchdialer
Swporta
Symfly
SyncroAd
Sys Detective +
Syscomdloader
Syscpy
Sysid
Sysil
System Process
System Soap Pro
System Spy
System Supervisor
System1060
System61
SystemDoctor 2006
SystemSearch
SystemStable
SystemVXD Dialer
Sysupd