Presented by: Nandor T. Szots Senior Programmer, EverQuest II nszots@soe.sony

1. Spam filtering in MMOs Presented by: Nandor T. Szots Senior Programmer, EverQuest II nszots@soe.sony.com Sony Online Entertainment

2. Overview • Introduction • Why is spam such a large problem in MMOs • Technical details of EQII’s filtering solution • MMO specific filtering techniques

3. Introduction • An MMO with 100k-500k subscribers can expect between 10,000 to 1 million spam messages to be sent to it’s players per day. • Helps to compromise fair game play • Gives an advantage to players willing to use third-party RMT sites. • Leads to loss of subscriptions • Generates no revenue for the developers

4. Why is spam such a large problem in MMOs • Third-party RMT is estimated to be a $2 billion / year business • 30% of MMO players are estimated to be involved as either buyers or sellers • Unlimited resources generated by the game • Access to resources using repetitive and scriptable tasks

5. Technical details of EQII’s filtering solution Naive Bayes Classifier • Each word is considered independently of the phrase • Allows for a simple DB • Uses a simple formula to determine spam probability • ln( p(S) / p(¬ S) ) in the case of MMOs can be dynamic based on player/account information

6. Technical details of EQII’s filtering solution Creating a DB of words • EQII DB • ~122,000 lines which is ~1 million words of good data • ~200 lines which is ~4,500 words of bad data • Much fewer types of spam messages creates this delta • Large ‘good’ data set makes it harder for spammer to pollute your data • Glue words ‘the’, ‘a’, ‘an’, ‘it’ etc. can be ignored • Words should only count once in any statement • Good idea to split out currency, game currency, etc. before processing

7. Technical details of EQII’s filtering solution Typical spam message examples from EQII • Typical messages pre-spam filtering: “Safe Gold,Fast power leveling,Special service of gold farming. Enjoy the fun we give you and your guild at www.spamworker.com” • Typical spam message today: “Stick to buy 1000 gold per-day for 5214 weeks on our site, you will be 100 years old, and become the strongest person in the game forever!” “Visit \/\/w\/\/.s###w0rk3r.c0/\/\, ###=pam, 3=e”

8. Technical details of EQII’s filtering solution Examples of applying the filter to real-world messages • Example DB and test phrases can be found on my website: http://nandor.szots.com • We will use two phrases with similar wording one which is spam and one which is not and show how the filter processes each

9. Technical details of EQII’s filtering solution Non-Spam message: “Hello, what’s up? Did you see how gold the sun was? Lets go power level!” • Filter is passed the phrase as follows: “hello what’s up did you see how #GAMECUR# the sun was lets go power level”

10. Technical details of EQII’s filtering solution • Filter processes each word: • Final value: -4.97 => Not Spam!

11. Technical details of EQII’s filtering solution Spam message: “Hello! Welcome to www.buygold.com. Power leveling, and fast safe gold!” • Filter is passed the phrase as follows: “hello welcome to www buygold com power leveling and fast safe#GAMECUR#”

12. Technical details of EQII’s filtering solution • Filter processes each word: • Final value: 28.45 => Spam!

13. MMO specific filtering techniques Techniques to allow cross-game implementation • Keyword replacements • In-game currencies • Genre-specific concepts • Real world monetary values • Dynamic modification of starting probabilities • Source and Destination filtering capabilities

14. MMO specific filtering techniques Looking at our probability one more time: • Need to make changes that do not effect mathematical correctness of the formula. • Best approach is to modify: ln( p(S) / p(¬ S) ) • Account Age • Account Type / Payment Type • IP Address • Character Age • Character Level • These should all be computed from real-world values like the word DBs

15. MMO specific filtering techniques MMO Advantages • Use your community to your advantage • Allow for real-time marking of spam and non-spam messages • Update word DBs frequently (once an hour or more) • Lots of additional information about message senders and reporters • Social relationships (guilds, groups, friends, etc.)

16. MMO specific filtering techniques MMO Disadvantages • Spammers can pre-test their messages • Minimize this by using ip, account, billing, etc. information • Spammers can try to weight their messages down by reporting them as not-spam • Create strict rules for accepting player reports to minimize spammers ability to weight your filter • It is important to create as much misdirection as possible

17. Q&A Questions & Answers