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Cheating at Multiplayer Online Games

Cheating at Multiplayer Online Games. Bruce Maggs (with some slides from An-Cheng Huang). A small confession…. Your professor is a notorious cheater. PLATO Computer System. PLATO IV Developed by the University of Illinois and the Control Data Corporation 1961 timesharing PLATO II begins

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Cheating at Multiplayer Online Games

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  1. Cheating at Multiplayer Online Games Bruce Maggs (with some slides from An-Cheng Huang)

  2. A small confession… Your professor is a notorious cheater

  3. PLATO Computer System • PLATO IV Developed by the University of Illinois and the Control Data Corporation • 1961 timesharing PLATO II begins • 1964 invention of plasma panel • 1968 PLATO IV begins • Spun off as “NovaNET” late 1980’s • Revived at www.cyber1.org

  4. Innovations • first LARGE on-line community • invention of the plasma panel • multimedia • “personal notes” – email • “group notes” – newsgroups • “consulting mode” – desktop sharing • widely used “term talk” (like Unix talk) • Shared memory enabled multiplayer games • IBM correctly attributes Lotus Notes to PLATO

  5. Hardware • Control Data mainframes designed by Seymour Cray • Cyber 70, 176, CDC 6600, 7600 • Magnetic core memory • 60-bit words, 6-bit characters • One’s-complement arithmetic • Up to 1000 simultaneous users • (NovaNET originally ran on Alpha processor)

  6. PLATO IV Terminal • 512x512 plasma panel • 1200 baud connection to mainframe • Stream of commands for displaying text and symbols, and for drawing lines https://digitalanalogues.wordpress.com/2011/04/22/it-really-is-deja-vu-all-over-again/

  7. Multiplayer Games • Dungeons and Dragons • e.g., oubliette, avatar • Space • e.g., spasim, empire • Warfare • e.g., airfight, panther

  8. Empire

  9. Empire Basics • I am  shrike , a proud Klingon / Kazari • Becoming a member of the Federation, a Vulcan/Orion, or a Romulan is equivalent to turning in your private key • The goal is to conquer the universe • Ship fires phasers, photon torpedos • Firing at correct angle inflicts more damage. To fire phasers at angle 233, type “f 233 NEXT” • Ship makes a hyperjump when you replot the screen, based on time since last replot

  10. Empire

  11. The Clone Brothers • I built a device that you plugged a keyboard into, and then it plugged into two separate PLATO IV terminals • Small circuit waited for both terminals to acknowledge keystroke before telling keyboard • Why? Fly two ships to same location in empire, then have double the firepower! • Nicknamed the “Clone Brothers” device migrated to different clusters of PLATO terminals around campus at U of I

  12. PLATO V Terminal • Plasma panel and CRT versions • Same 512 x 512 display • 8080 processor implemented all graphics

  13. PLATO V Terminal From http://plato.filmteknik.com/

  14. Empire Bot • 8080 had access to stream of commands sent to terminal from mainframe • I wrote assembly code to determine angles to enemies on the screen (using an arctan look-up table) • Program displayed exact angle above each enemy, with keyboard shortcuts to fire phasers or torpedos at that angle • Also displayed a growing ellipse around ship to indicate distance of hyperjump • Possibly the first shooter-game bot - 1979? (“shoot’ em up” or “arcade shooter” genre)

  15. Avatar

  16. Avatar Basics • Players join different guilds, e.g., fighter, magician, cleric, and gain different capabilities • Players form groups and enter the dungeon together to fight monsters and gather treasures • At one time possibly most popular multi-player on-line game in the world • Co-authored with David Sides and Andrew Shapira, with help from many others • My current character is dead on level one

  17. Avatar

  18. Duplicating Magical Items • Strategy: give all of your magical items and gold to a friend, the crash the game before the changes to your character are recorded to disk! • Negative: “unfair” and throws the game economy out of whack • Positive: we quickly find out about serious bugs

  19. Best Consulting Gig Ever • I am hired by Jagex, maker of Runescape to document that third-party bots really work • My character is exempted from being banned for using bots • My kids complain that I am a cheater

  20. Runescape

  21. How do the bots work? • Runescape is a Java applet • Bot maker provides Java applet container • Bot does not scrape the screen, but instead examines the byte code • Bot determines position on screen of character, objects, etc.

  22. Anti-Bot Measures • Code is rearranged in different instances of applet • Ultimately, all data stored in one master array, permuted in random order, killing bots! • Many players quit when bots were defeated

  23. First-Person Shooter Gamesplayed over the Internet

  24. forward render player1 at (x1,y1) forward Impact of Latency • Naïve approach: dumb client (e.g., Empire)   render player1 at (x1,y1)  Player1 Response time for player: round-trip to server + server processing

  25. render player1 at (x1,y1) render player1 at (x1,y1) render player1 at (x4,y4) render player1 at (x1,y1) forward render player1 at (x1,y1) forward forward forward forward Updating Position Locally    Player1 Other players see old position.

  26. Now Int. delay Now Now Update3 (x3,y3) Update2 (x2,y2) Predicting Where You Are • Updates about other players’ locations not continuous • Extrapolation (dead reckoning) • At last update, player2 is at (x1,y1) facing N with speed S It should be at (x2,y2) now • Not good: in FPS, player movement very non-deterministic • Interpolation • Impose an “interpolation delay”for rendering Update1 (x1,y1) time

  27. Lag Compensation • Interpolation introduces a fixed lag (int. delay) • E.g., always see where players were 100 ms ago • Need to lead the target when aiming • Require players to extrapolate! • Server-side lag compensation • Server uses the old location to compute hit/miss • Allows natural aiming/shooting • Possible weird experiences for players being fired upon (e.g., being told that you died some time ago) tradeoff for better game play

  28. P3   P3 P2 (3 ms) P3 (1 ms) P1    P1 P2  P2 Fair Message Exchange P1 (4 ms) • [Guo et al. NG03] • Look at “fairness” in client-server games room

  29. t=8 t=11 t=19 P2 3 P3 P1 1 4 Fair Message Exchange (2) t=0 • Different latencies can make the game “unfair” Server P1 (RTT 5) P2 (RTT 10) P3 (RTT 15) time

  30. P3 P2 P2,3,18 P2,3,18 P3,1,16 P2,3,18 t=8 t=11 t=16 t=18 t=19 P2 3 P3 P1 1 4 Fair Message Exchange (3) • Fair-ordering delivery without synchronized clocks(a simple case) t=0 Server P1 (RTT 5) P2 (RTT 10) P3 (RTT 15) Server waits (here 15) before performing action. Ordering based on response time.

  31. Cheating Strategy • Introduce artificial delay between client and server • Lie about how long it took to respond (or take advantage of server thinking update was received last) • Server will think client was first to shoot, even though it receives message last

  32. Texture Hacks! transparent

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