I recently updated the default ExpressionEngine blacklist for user agents with a list from AskApache.com. If you have problems with EE spam, try adding these user agents to your Blacklist module.
Note that many of these programs are very popular with spammers, but can be used by real users as well. As usual, use your own judgment when updating the blacklist.
Note that some names overlap, e.g. “Grabber” would also catch all the names ending with the same word. I’ve still included the full names to make it easier for you to tailor the list to your own requirements.
[List edited Dec 5 to remove a few names that are too short to be used with the wildcard search within the user agent string that E uses.]
d-o-o-b-u.com (Remove the hyphens, EE caught this one as forum spam!)
AdultGods
AESOP_com_SpiderMan
Alexibot
Anonymouse
asterias
attach
BackDoorBot
BackWeb
Baiduspider
Bandit
BatchFTP
Bigfoot
Black.Hole
BlackWidow
BlowFish
BotALot
Buddy
BuiltBotTough
Bullseye
BunnySlippers
Cegbfeieh
CheeseBot
CherryPicker
ChinaClaw
Collector
Copier
CopyRightCheck
cosmos
craftbot
Crazy Browser
Crescent
Curl
Custo
DIIbot
DISCo
DittoSpyder
Download
Download Demon
Download Devil
Download Wonder
Downloader
dragonfly
Drip
EasyDL
ebingbong
eCatch
EirGrabber
EmailCollector
EmailSiphon
EmailWolf
EroCrawler
Exabot
Express WebPictures
Extractor
ExtractorPro
EyeNetIE
FileHound
FlashGet
flunky
Foobot
FrontPage
GetRight
GetSmart
GetWeb!
Go!Zilla
Go-Ahead-Got-It
Google Wireless Transcoder
gotit
Grabber
GrabNet
Grafula
Harvest
hloader
HMView
httplib
HTTrack
humanlinks
ia_archiver
IlseBot
Image Stripper
Image Sucker
Indy Library
InfoNaviRobot
InfoTekies
Intelliseek
InterGET
Internet Ninja
Iria
Jakarta
JennyBot
JetCar
JOC
JOC Web Spider
JustView
Jyxobot
Kenjin.Spider
Keyword.Density
larbin
LeechFTP
LexiBot
lftp
libWeb/clsHTTP
likse
LinkextractorPro
LinkScan
LinkWalker
LNSpiderguyt
LWP::Simple
lwp-trivial
Magnet
Mag-Net
MarkWatch
Mass Downloader
Mata.Hari
Memo
Microsoft URL Control
Microsoft.URL
MIDown tool
MIIxpc
Mirror
Missigua Locator
Mister PiX
moget
Mozilla.*NEWT
Mozilla/3.Mozilla/2.01
NAMEPROTECT
Navroad
NearSite
Net Vampire
NetAnts
Netcraft
NetMechanic
NetSpider
NetZIP
NextGenSearchBot
NICErsPRO
NimbleCrawler
Ninja
NPbot
Octopus
Offline Explorer
Offline Navigator
Openfind
OutfoxBot
PageGrabber
Papa Foto
pavuk
pcBrowser
PHP version tracker
pinappleproxy
Pockey
Popdexter
ProPowerBot/2.14
ProWebWalker
psbot
Pump
PycURL
QueryN.Metasearch
RealDownload
Reaper
Recorder
ReGet
RepoMonkey
RMA
Siphon
sitecheck.internetseer.com
SiteSnagger
SlySearch
SmartDownload
Snake
Snapbot
Snoopy
sogou
SpaceBison
SpankBot
spanner
Sqworm
Stripper
Sucker
SuperBot
SuperHTTP
Surfbot
suzuran
Szukacz/1.4
tAkeOut
Teleport
Teleport Pro
Telesoft
The.Intraformant
TheNomad
TightTwatBot
Titan
toCrawl/UrlDispatcher
TrackBack
True_Robot
turingos
TurnitinBot
TurnitinBot/1.5
URLy.Warning
W3CRobot
Vacuum
VCI
Web Image Collector
Web Sucker
Web.Image.Collector
WebAuto
WebBandit
Webclipping.com
WebCopier
WebEMailExtrac
WebEnhancer
WebFetch
WebGo IS
WebLeacher
WebmasterWorldForumBot
WebReaper
WebSauger
WebSite
Website eXtractor
Website Quester
Webster
WebStripper
WebWhacker
WebZIP
Wget
Whacker
Widow
WISENutbot
VoidEYE
wp-comments-post
WWW-Collector-E
WWWOFFLE
Xaldon
Xaldon WebSpider
Xenu
yourdomain.com
Zeus
Zyborg