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Activities pattern matching intrusion c ant de te c t

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activities pattern matching intrusion C an’t de te c t ne w attac ks Example: if (src_ip == dst_ip) then “land attack”
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Anomaly Detection activity measures 0 10 20 30 40 50 60 70 80 90 CPU Process Size normal profile abnormal probable intrusion Re lative ly hig h fals e  po s itive  rate    Ano m alie s  c an jus t be  ne w no rm al ac tivitie s .  Ano m alie s  c aus e d by o the r e le m e nt faults  E.g ., ro ute r failure  o r m is c o nfig uratio n, P2P  m is c o nfig uratio n Any pro ble m  ?
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Host-Based IDSs Us ing  O S  auditing  m e c hanis m s E.G ., BS M o n S o laris : lo g s  all dire c t o r indire c t e ve nts   g e ne rate d by a us e r s ys te m  c alls  m ade  by a pro g ram  (Linux) Mo nito ring  us e r ac tivitie s E.G ., analyze  s he ll c o m m ands Pro ble m s : us e r de pe nde nt Have  to  ins tall IDS  o n all us e r m ac hine s  ! Ine ffe c tive  fo r larg e  s c ale  attac ks
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The Spread of Sapphire/Slammer Worms
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Network Based IDSs At the  e arly s tag e  o f the  wo rm , o nly lim ite d wo rm   s am ple s .  Ho s t bas e d s e ns o rs  c an o nly c o ve r lim ite d IP s pac e ,  whic h m ig ht have  s c alability is s ue s . Thus  the y m ig ht  no t be  able  to  de te c t the  wo rm  in its  e arly s tag e Gateway routers Internet Our network Host based detection
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Network IDSs De plo ying  s e ns o rs  at s trate g ic  lo c atio ns E.G ., Pac ke t s niffing  via tcpdump at routers Inspecting network traffic  Watch for violations of protocols and unusual connection patterns Monitoring user activities Look into the data portions of the packets for malicious code May be easily defeated by encryption Data portions and some header information can be encrypted The decryption engine may still be there, especially for exploit
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Key Metrics of IDS/IPS Alg o rithm Alarm : A; Intrus io n: I De te c tio n (true  alarm ) rate : P(A|I) Fals e  ne g ative  rate  P( ¬ A|I) Fals e  alarm  (fals e  po s itive ) rate : P(A| ¬ I) True  ne g ative  rate  P( ¬ A| ¬ I) Arc hite c ture
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