A dynamic resource allocation decision model for IT security

Transcription

1 A dynamc resource allocaon decson model for IT secury Lof Hajjem 1, Salah Benabdallah 2, Fouad Ben Abdelazz 3 1 Graduae Suden, Insu Supéreur de Geson (ISG), Unversy of Tuns, Tuns, Tunsa (lof.hajjem@gmal.com) 2 Drecor of Insu Supéreur des Eudes Technologques en Communcaons de Tuns (Ise Com), Tuns, Tunsa (sba@supcom.rnu.n) 3 Professor, College of Engneerng, Amercan Unversy of Sharjah, Sharjah, Uned Arab Emraes. (fabdelazz@aus.edu) ABSTRACT Today, wh he connued growh n usng nformaon and communcaon echnologes (ICT) for busness purposes, busness organzaons become ncreasngly dependen on her nformaon sysems. Thus, hey need o proec hem from he dfferen aacks eplong her vulnerables. To do so, he organzaon has o use secury echnologes, whch may be proacve or reacve ones. Each secury echnology has a relave cos and addresses specfc vulnerables. Therefore, he organzaon has o pu n place he approprae secury echnologes se ha mnmzes he nformaon sysem s vulnerables wh a mnmal cos. Ths b-objecve problem wll be consdered as a resources allocaon problem (RAP) where secury echnologes represen he resources o be allocaed. However, he se of vulnerables may change, perodcally, wh he connual appearance of new ones. Therefore, he secury echnologes se should be fleble o face hese changes, n real me, and he problem becomes a dynamc one. In hs paper, we propose a harmony search based algorhm o solve he b-objecve dynamc resource allocaon decson model. Ths approach was compared o a genec algorhm and provded good resuls. Keywords: Dynamc resource allocaon, IT secury, Harmony search, Mulobjecve opmzaon 1. INTRODUCTION Securng he nformaon sysem s an mporan ask for an organzaon. In fac, he connued growh n usng nformaon and communcaon echnologes (ICT) for busness purposes makes busness organzaons ncreasngly dependen on her nformaon sysems. Any successful aack wll cause a serous loss of daa, servces, asses, busness operaons, ec. [7]. These aacks, whch can be made by nernal or eernal enes, eplo he vulnerables ha may es n he nformaon sysem. To face hese aacks, he organzaon has o overcome he nformaon sysem s vulnerables usng secury echnologes. Each one of he secury echnologes addresses specfc vulnerables. Therefore, he organzaon has o pu n place he approprae se of secury echnologes ha mnmzes he vulnerables of he nformaon sysem. Ths problem can be saed as a resource allocaon problem (RAP). A RAP s he process of allocang resources among varous projecs or busness uns wh a mamum prof and a mnmum cos [1]. In he proposed model, he secury echnologes represen he resources o be allocaed o he nformaon sysem o overcome s vulnerables. However, he se of vulnerables may change perodcally wh he connual appearance of new ones. Therefore, he se of secury echnologes needs o be fleble o face hese changes. Thus, he problem, here, becomes a dynamc one, as he se of mplaned secury echnologes should be redefned n real me o face he new vulnerables appearng n he nformaon sysem. As a resul, he suded problem wll be saed as a dynamc resource allocaon problem (DRA). In addon, n hs problem we have o consder he cos of each secury echnology. Thus, he organzaon wans o mnmze he overall cos of he secury echnologes used o secure s nformaon sysem. The problem becomes a b-objecve one, where we have, o mnmze he number of vulnerables n he nformaon sysem wh he mnmum cos. Ths paper wll be saed as follows: he problem of nformaon sysem secury wll be descrbed, n he frs secon. Ne, n secon 3, he problem of IT secury, saed as a b-objecve dynamc resource allocaon problem, wll be defned and formulaed. Then, he harmony search approach wll be presened. Secon 5 wll be devoed o he adapaon of wo resoluon approaches, he harmony search algorhm and he genec algorhm. And n he las secon, a comparson of he wo approaches s descrbed. The paper fnshes by a concluson. 2. INFORMATION SYSTEM SECURITY 2.1 Why securng nformaon sysems?

2 The connued growh n he use of nformaon echnologes for busness purposes makes busness organzaons ncreasngly dependen on her nformaon sysems. In fac, he evoluon of nework echnologes perms an easy communcaon beween dfferen parners, ndependenly of her locaons. The communcaon may epose he parner s nformaon asses o dangerous hreas ha eplo he nformaon sysem vulnerables. An nformaon asse s defned as anyhng of value o he organzaon. I can be eher angble or nangble. Tangble asses nclude physcal nfrasrucure (such as servers and nework nfrasrucure) and sofware elemens of he nformaon sysem. Inangble asses nclude busness or oher dgal nformaon of value o he organzaon (such as bankng ransacons, neres calculaons, produc-developmen plans and specfcaons), organzaon knowledge, company repuaon and he nellecual propery sored whn he organzaonal sysem [7]. As can be seen, he asses are of grea mporance for he organzaon. However, hey are eposed o mulple hreas ha can be eher naural dsasers or human acs. The hreas caused by human can be non-malcous (e.g., mssng secury paches, openng a malcous emal, ec.) or malcous ones (e.g., hef, loss or desrucon of an organzaonal asse, unauhorzed access o he nework servces, nfecon wh malcous code, nsder hreas, hackers, errorss, ec.). Therefore, he organzaons need o secure her nformaon sysem agans he hreas ha may eplo a large number of vulnerables. In fac, s repored ha he secury research communy denfes and publshes on an average of 40 new secury vulnerables per week on varous producs, from operang sysems, daabases, applcaons o even neworkng devces [2]. Anoher sudy of he Compuer Emergency Response Team/Coordnaon Cener (CERT/CC) ndcaes ha he number of found vulnerables was from 345 o 5990 n he decade of [5]. Due o he large number of vulnerables, he number of aacks s growng n an mmeasurable way. In fac, he number of evens repored o CERT/CC was 2573 n In 2003, was n an asonshng number of secury ncdens. 2.2 Informaon secury echnologes Securng he nformaon sysems becomes a prory for he organzaons. In fac, any successful aack on he nformaon sysem and s evenual crash could resul n a serous loss of daa, servces and busness operaons. Therefore, he organzaons need o proec her nformaon sysems agans he evenual aacks ha may occur. To do so, hey need o use effcen nformaon secury echnologes ha perm he proecon of nformaon and mnmze he rsk of eposng o unauhorzed pares. There are wo famles of secury echnologes, proacve and reacve ones. A proacve nformaon secury echnology s a echnque ha akes prevenave measures n a bd o secure daa or resources before a secury breach can occur [8] (e.g. crypography, dgal sgnaure, vrual prvae nework, ec.). Whereas, a reacve nformaon secury echnology performs prevenve measures n a bd o secure daa or resources as soon as a secury breach s deeced [8] (e.g. frewalls, passwords, nruson deecon sysems, ec.). Each one of he secury echnologes addresses specfc vulnerables and has a relave cos. Thus, he organzaon has o pu n place he approprae se of secury echnologes ha mnmzes he nformaon sysem s vulnerables wh he mnmum cos, whch becomes a bg dlemma for. In fac, accordng o he Deparmen of Trade and Indusry (DTI) 2006 survey he average s around 4 o 5% of he organzaon s IT budge beng spen on secury soluons [7]. In hs paper, he problem of securng nformaon sysems wll be saed as a B-objecve Dynamc Resource Allocaon Problem. Ths decson model wll be defned, n he ne secon, and s mahemacal formulaon wll be descrbed. 3.1 Problem defnon 3. DECISION MODEL The problem of securng nformaon sysems wll be suded, n hs paper, as a RAP where he secury echnologes represen he se of resources. The problem can be saed as follows: Le V be he se of vulnerables of an nformaon sysem where: 1, f vulnerably s used by he nformaon sysem V of he organzaon, 0, Oherwse. Le S be a se of M secury echnologes ha may be pu n place by an organzaon where: S j 1, f secury js used by he nformaon sysem of he organzaon, 0, Oherwse. Each secury echnology s j has an assocaed cos C j. And le SV be he secury/vulnerably mar such ha: 1, f vulnerably s covered by secury j, SV [, j] 0, Oherwse. The problem, here, s o fnd he se of secury echnologes ha mnmzes he number of vulnerables of he nformaon sysem wh he mnmal cos. Ths problem wll be suded as a b-objecve one where we

3 have o: (1) Mnmze he number of vulnerables a any me perod, (2) Mnmze he oal cos of he secury echnologes o be used. In addon, he problem wll be suded dynamcally n order o be able o overcome he new vulnerables ha may appear, a each me. In fac, he organzaon needs o adap he se of mplaned secury echnologes, n real me, o he dfferen crcumsances ha may happen o he nformaon sysem, and wh he mnmal cos. 3.2 Mahemacal formulaon The problem of securng nformaon sysems consss on fndng he opmal combnaon of secury echnologes ha mnmzes he nformaon sysem s vulnerables, wh he mnmal cos. As defned n he las paragraph, s a b-objecve problem ha wll be saed as dynamc resource allocaon problem. Le R be he se of resdual vulnerables, where r s calculaed as follows: f v = 0 hen r = 0 f v = 1 and j s j = 1 and SV [, j] = 1, hen r = 0. f v = 1 and SV [, j] = 0 j s j = 1, hen r = 1. Where he frs condon ndcaes ha f vulnerably v s no presen n he organzaon s nformaon sysem (v =0) hen s no a resdual vulnerably. The second one sgnfes ha f vulnerably v s presen n he organzaon s nformaon sysem (v =1) and here ess a secury echnology s j used by he organzaon ha addresses hen s no a resdual vulnerably (r = 0). And he las equaon sgnfes ha f vulnerably v s presen n he organzaon s nformaon sysem (v =1) and here s no used secury echnology s j addressng hen s a resdual vulnerably (r =1). Therefore, he problem can be formulaed as follows: Subjec o Mn N ( ) r, 1,..., T R n v 1 (1) MnC ( S) C ( S ) c * s (2) n n j 1 qm qm, m 1,..., M, (3) f ( R 1, IS, S 1) IS 1 (4) r 0,1, 1,..., nv, 1,..., T (5) s j 0,1, j 1,..., ns, 1,..., T (6) Where n v and n s are he numbers of vulnerables and secury echnologes, respecvely. T represens he number of me perods. R s he se of resdual vulnerables a me perod. IS s he se of mplaned secury echnologes. And, S s he se of secury j j echnologes ha may be used by he organzaon. In hs formulaon, equaons (1) represen he objecve funcons of mnmzng he se of resdual vulnerables a each me perod. Ne, equaon (2) s he objecve funcon of mnmzng he overall cos of he secury echnologes. Then, equaons (3) are he resources sasfacon consrans. Fnally, equaon (4) ndcaes ha he se of mplaned secury echnologes a he (+1) h me perod s a funcon of he se of resdual vulnerables a he ( + 1) h me perod (R +1 ), he se of mplaned secury echnologes a he () h me perod (IS ), and he se of secury echnologes ha may be used by he organzaon a he (+1) h me perod (S T+1). For hs problem, a new me perod has o be consdered where a leas a new vulnerably s deeced n he organzaon s nformaon sysem. Ths problem was no well-suded n he leraure and few approaches were developed for some oher problems close o. Among hem, we can noe a genec algorhm ha was proposed o solve he sac b-objecve resource allocaon problem [4]. In addon, some mercs for quanfyng an ICT secury nvesmen are descrbed n [7]. 4. HARMONY SEARCH ALGORITHM 4.1 Algorhm descrpon The harmony search (HS) algorhm s developed o mae he muscan behavor ryng o mprove s muscal harmony pracce afer pracce usng he se of he pches played by each nsrumen. Ths process can be compared o he one of opmzng an objecve funcon eraon by eraon usng he values assgned for decson varables [6]. The HS algorhm ncludes fve seps: parameers nalzaon, he harmony memory (HM) nalzaon, he new harmony mprovsaon, he harmony memory updae and he check of ermnaon creron [3]. 4.2 Sep 1: Parameers nalzaon In hs sep, he opmzaon problem s specfed: Mnmze (or Mamze) f(); X, =1, 2,, N where: f() s an objecve funcon s he soluon vecor composed of decson varables X s he se of possble values for decson varable X = { (1), (2),..., (K)} for dscree varables N s he number of decson varables K s he number of possble values for each dscree varable The algorhm parameers are also specfed durng hs sep such as: The harmony memory sze(hms): s he number of soluon n he memory

4 The harmony memory consderng rae (HMCR); 0 HMCR 1; hs ypcal values range from 0.7 o 0.99 The pch adjusmen rae (PAR); 0 PAR 1; hs seleced values range s from 0.1 o 0.5 Improvsaons number or objecve funcons number 4.3 Sep 2: Harmony memory nalzaon Durng hs sep, HMS soluons are randomly generaed o form he harmony memory. Each decson varable () selecs a value from s correspondng ls (X). Then he fness values are calculaed for he generaed soluons (equaon 7) f( ) f( ) (7) HMS 1 HMS 1 HMS 1 HMS 1 HMS-1... f( ) 1 HMS HMS HMS HMS HMS... f( ) Sep 3: New harmony mprovsaon In hs sep, a new harmony vecor s generaed from he HM based on memory consderaons, pch adjusmens, and randomzaon, as shown n equaon 8: X, Where, HMCR (harmony memory consderaon rae) s he probably of choosng a value from he soluons sored n he HM. Whle (1- HMCR) s he probably of randomly choosng one feasble value from he se of all possble values for he correspondng decson varable. Whle mprovsng he new harmony, each value chosen from HM s eamned o deermne wheher should be pch-adjused. Ths procedure uses he PAR parameer ha ses he rae of adjusmen for he pch chosen from he HM as follows: 1 2 HMS ',,..., wh probably HMCR ' (8) ', wh probably (1- HMCR) Yes, wh probably PAR, Pch adjusng decson for ' (9) No, wh probably (1- PAR). The value of (1 - PAR) ses he rae of dong nohng. If he pch adjusmen decson for s YES, s replaced as follow: (10) where bw s an arbrary dsance bandwdh and rand() s a random number beween 0 and 1 or beween -1 and Sep 4: Harmony memory updae If he new harmony vecor s beer han he wors harmony n he HM, judged n erms of he objecve funcon value, he new harmony s ncluded n he HM and he esng wors harmony s ecluded from he HM. 4.6 Sep 5: Termnaon creron check If he soppng creron s sasfed, compuaon s ermnaed. Oherwse, Seps 3 and 4 are repeaed. The soppng crera may be eher mamum number of mprovsaons or a mamum number of eraon whou mprovemen of he soluon. 5. RESOLUTION APPROACHES To solve he problem of securng, n real me, an nformaon sysem agans he dfferen aacks ha may happen, wo mea-heurscs were developed, a harmony search algorhm and genec algorhm. These wo approaches are composed of wo phases, he sac and he dynamc one. The sac phase s appled for he nal sysem sae (=0). And he dynamc one s appled o face he new vulnerables ha may be found n he sysem. I should ake no consderaon he curren secury plan and he new secury echnologes ha may appear. 5.1 Harmony search algorhm The proposed HS algorhm for he sac phase can be descrbed as follows: Sep1. Parameers nalzaon: The mprovsaons number s equal o 2, as he suded problem s a bobjecve one. In addon, he harmony memory wll conan he non-domnaed soluons and s sze (HMS) wll be se o 50. The raes HMCR and PAR wll be se o 95% and 30%, respecvely. Sep2. Harmony memory nalzaon: In hs sep, 50 dfferen soluons wll be randomly generaed. The soluons generaon process wll be as follows: he secury echnologes wll be randomly seleced one by one unl a consrucon-soppng creron s verfed,.e. he oal cos eceeds a value Cma or he number of resdual vulnerables becomes less han a bound Nvmn. In order o ge a beer soluon qualy, a secury echnology s added only f covers a leas a resdual vulnerably. In addon, and whle generang he HM a new secury/vulnerably mar, noed SV wll be

5 consruced. I wll presen for each secury echnology he vulnerables ha covered, effecvely n he sysem. Tha s, for any secury echnology chosen n he consrucon process, he vulnerables ha were covered by wll be recorded. Sep3. New harmony mprovsaon: In hs sep, a new harmony s generaed based on he HMCR and PAR raes. The generaon process can be descrbed as follows: A resdual vulnerably s randomly seleced and accordng o he HMCR value, a secury echnology wll be chosen eher from SV or from SV,.e: SV', wh probably HMCR ' s seleced from (11) SV, wh probably (1- HMCR) Then, each me a secury echnology s seleced from SV, a pch adjusmen s performed wh a probably PAR. I consss on selecng a secury echnology from he ones ha was no appled for he curren vulnerables and f does no es, he selecon wll be done among he ones addressng he curren vulnerably. Sep4. Harmony memory updae: The generaed soluon wll be added o he HM f s no domnaed by any esng soluon. In addon, f s added o he HM, all he soluons domnaed by he new soluon wll be elmnaed. Sep5. Termnaon creron check: The Seps 3 and 4 are repeaed unl here s no mprovemen of he HM for 50 successve eraons. And he soluons of he HM wll consue he se of non-domnaed soluons. I conans he soluons ha can be adaped o he curren nformaon sysem. The proposed HS for he dynamc phase dffers from he one of he sac phase n Sep2, he harmony memory nalzaon. In fac, he process of generang he 50 dfferen nal soluons can be descrbed as follows: 40 soluons wll be generaed by randomly selecng one from he se of non-domnaed soluons, o whch oher secury echnologes are added unl he consruconsoppng crera s sasfed. The 10 remanng soluons are generaed randomly as descrbed n Sep2, n order o make a beer dversy n he search space. 5.2 Genec algorhm: The genec algorhm s a well-known mea-heursc ha was appled o a wde varey of sngle and mulobjecve opmzaon problems. I s characerzed of 2 man operaors, he crossover and he muaon operaors. The crossover operaor s appled o generae chldren from a par of parens seleced from he curren populaon. Each paren conrbues by a poron of s genec make-up o each chld. And he muaon operaor randomly changes a ny amoun of genec nformaon n each chld. The sac phase of he proposed genec algorhm can be descrbed as follows: An nal populaon of 50 soluons s generaed, smlarly o he HS algorhm (refer o Sep2). Then, wh a probably of 90%, a wo pon crossover operaor s appled o wo randomly seleced soluons from he populaon, o ge wo chldren. If he consrucon-soppng creron s no sasfed for a chld, he consrucon process wll connue n he same way of he consrucng he nal populaon process. Ne, wh a probably of 10%, he muaon operaor s appled o each chld. I consss on elmnang one of he secury echnology used by he soluon and connue he consrucon process by he remanng secury echnologes. Fnally, a chld s added o he populaon f s no domnaed by any esng soluon and f s added, all he soluons domnaed by wll be elmnaed. Ths process sops f here s no mprovemen of he populaon for 50 successve eraons. The fnal populaon wll consue he se of non-domnaed soluons. The dynamc phase s dencal o he one of he HS algorhm. 6. COMPUTATIONAL RESULTS In hs secon, he performances of he wo approaches are verfed for dfferen problem szes. To do so, he quales of non-domnaed soluons generaed by he wo echnques for dfferen nsances are evaluaed accordng o he C merc (coverage of wo ses) ha can be defned as follows [9]: Le A, B be wo non-domnaed soluons ses. The measure C maps he ordered par (A, B) no he range [0, 1]: b B/ aa: a domnaesb C ( A, B) (12) Ths merc calculaes, for a non-domnaed soluons se B, he percenage of soluons ha are domnaed by a leas a soluon of he non-domnaed soluons se A. When esng he wo approaches, s supposed ha here are, nally, 25 vulnerables and 40 secury echnologes, where each secury echnology addresses specfc vulnerables (he SV mar). Then, n each me perod new vulnerables and secury echnologes are added o he sysem and he SV mar s updaed. I s supposed ha a new vulnerably can be covered by an esng secury echnology or by a new one. In addon, a cos mar s generaed n such a way ha more s he number of covered vulnerables by a secury echnology, hgher s s relave cos. And fnally, s B

6 supposed ha oal cos allowed (Cma) s and he number of resdual vulnerables (Nvmn) should no be more han 3. The wo algorhms are eecued for 11 me perods and he resuls of he comparson are summarzed n Table1, where he row T represens he me perods. The row Sze s a par (secury, vulnerably) gvng he number of he secury echnologes ha may be used by he organzaon and he number of nformaon sysem s vulnerables. The column C(HS,GA) presens he frequency by whch he oucome of genec algorhm s domnaed by soluons generaed by he HS algorhm. The column C(GA,HS) gves he frequency by whch he oucome of he HS algorhm s domnaed by soluons generae by he GA. And he row Common Soluons gves he number of smlar soluons found by he wo algorhms. To deal he nformaon gven by able1 we ake as eample he me perod 1. There are 35 vulnerables n he nformaon sysem and he organzaon has o selec s secury plan among 55 secury echnologes. The resuls generaed by he 2 algorhms ndcae ha 33% of he soluons generaed by he GA are domnaed by a leas a soluon generaed by he HS algorhm. Whereas, here s no soluon generaed by he HS algorhm domnaed by he non-domnaed soluons of he GA. And here are 2 common soluons generaed by he wo algorhms. The resuls presened n Table1 ndcae ha he HS algorhm generaes n mos mes beer resuls han he GA. In fac, among he 11 me perods, he C measure value was n he favor of he HS algorhm for 8 mes agans once for he GA and 2 equales. Table1: Comparson of he wo approaches n erm of C measure values Tme Common Sze C(HS,GA) C(GA,HS) perod Soluons 0 (25, 40) 25% 0% 3 1 (35, 55) 33% 0% 2 2 (45, 70) 75% 25% 0 3 (55, 85) 50% 0% 2 4 (65, 100) 0% 0% 4 5 (75, 115) 0% 50% 2 6 (85, 130) 50% 0% 2 7 (95, 145) 100% 0% 0 8 (105, 160) 75% 25% 0 9 (115, 175) 50% 0% 2 10 (125, 190) 50% 50% 0 model n order o proec, n real me, he organzaons from he aacks frequenly occurrng. To solve hs problem, a harmony search algorhm and a genec algorhm were proposed. A comparson of he wo approaches, accordng o he C measure was esablshed. I ndcaes ha he HS algorhm gves beer resuls n mos me perods of he opmzaon process. REFERENCES [1] Ch-Mng, L. And Msuo G. Mulobjecve resource allocaon problem by mulsage decson-based hybrd genec algorhm, Appled Mahemacs and Compuaon, Vol. 187, No. 2, pp , [2] Eschelbeck, G., The Laws of Vulnerables: Whch secury vulnerables really maer?, Informaon Secury Techncal Repor., Vol. 10, No. 4, pp , [3] Geem, Z.W., Km, J.H., and Loganahan, G.V. A new heursc opmzaon algorhm: harmony search, Smulaon, Vol. 76, No. 2, pp , [4] Gupa, M., Rees, J., Chaurved, A., and Ch, J. Machng nformaon secury vulnerables o organzaonal secury profles: a genec algorhm approach, Decson Suppor Sysems, Vol. 41, No. 6, pp , [5] La, Y. and Hsa, P. Usng he vulnerably nformaon of compuer sysems o mprove he nework secury, Compuer Communcaons, Vol. 30, No. 9, pp , [6] Lee, K.S., and Geem, Z.W. A new srucural opmzaon mehod based on he harmony search algorhm, Compuers and Srucures, Vol. 82, No. 9-10, pp , [7] Rok, B., and Borka, J. B. Towards a sandard approach for quanfyng an ICT secury nvesmen, Compuer Sandards & Inerfaces, Vol. 30, No. 4, pp , [8] Vener H. S., and Eloff J. H. P., A aonomy for nformaon secury echnologes, Compuers & Secury, Vol. 22, No. 4, pp , [9] Zzler, E., Evoluonary Algorhms for Mulobjecve Opmzaon: Mehods and Applcaons, PhD hess, Swss Federal Insue of Technology, Zurch, CONCLUSION In hs paper, he problem of securng nformaon sysems was suded as b-objecve problem where we have o mnmze he nformaon sysem s vulnerables wh a mnmum cos. Ths problem was defned and formulaed as a dynamc resource allocaon decson