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Network Security

Network Security

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Network Security

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  1. Network Security

  2. Malware - Summary • Virus: • program which is included in other programs and can reproduce itself • Worm: • program that distributes itself via the network • Trojan horse: • program that hides additional functionality useful for an adversary • Rootkit: • faked OS providing additional functionality (for an attacker) but simulating original OS (almost) perfectly: e.g. faked versions of ls, ps, nstat, etc.

  3. Vulnerabilities all over the time • see Recent CVE Vulnerabilities CVE-2006-3349  Publish Date: 7/3/2006   Multiple SQL injection vulnerabilities in SmS Script allow remote attackers to execute arbitrary SQL commands via the CatID parameter in (1) cat.php and (2) add.php. CVE-2006-3348  Publish Date: 7/3/2006   Multiple SQL injection vulnerabilities in HSPcomplete 3.2.2 and 3.3 Beta and earlier allow remote attackers to execute arbitrary SQL commands via the (1) type parameter in report.php and (2) level parameter in custom_buttons.php. CVE-2006-3347  Publish Date: 7/3/2006   SQL injection vulnerability in index.php in deV!Lz Clanportal DZCP 1.3.4 allows remote attackers to execute arbitrary SQL commands via the id parameter. CVE-2006-3346  Publish Date: 7/3/2006   SQL injection vulnerability in tree.php in MyNewsGroups 0.6 allows remote attackers to execute arbitrary SQL commands via the grp_id parameter. CVE-2006-3345  Publish Date: 7/3/2006   Cross-site scripting (XSS) vulnerability in AliPAGER, possibly 1.5 and earlier, allows remote attackers to inject arbitrary web script or HTML via a chat line. CVE-2006-3344  Publish Date: 7/3/2006   Siemens Speedstream Wireless Router 2624 allows local users to bypass authentication and access protected files by using the UPnP (Universal Plug and Play)/1.0 component. CVE-2006-3343  Publish Date: 7/3/2006   PHP remote file inclusion vulnerability in recipe/cookbook.php in CrisoftRicette 1.0pre15b allows remote attackers to execute arbitrary PHP code via a URL in the crisoftricette^parameter. CVE-2006-3342  Publish Date: 7/3/2006   Cross-site scripting (XSS) vulnerability in index.php in Arctic 1.0.2 and earlier allows remote attackers to inject arbitrary web script or HTML via the query parameter in a search cmd. CVE-2006-3341  Publish Date: 7/3/2006   SQL injection vulnerability in annonces-p-f.php in MyAds module 2.04jp for Xoops allows remote attackers to execute arbitrary SQL commands via the lid parameter. CVE-2006-3340  Publish Date: 7/3/2006   Multiple PHP remote file inclusion vulnerabilities in Pearl For Mambo module 1.6 for Mambo, when register_globals is enabled, allow remote attackers to execute arbitrary PHP code via the (1) phpbb_root_path parameter in (a) includes/functions_cms.php and the (2) GlobalSettings[templatesDirectory] parameter in multiple files in the "includes" directory including (b) adminSensored.php, (c) adminBoards.php, (d) adminAttachments.php, (e) adminAvatars.php, (f) adminBackupdatabase.php, (g) adminBanned.php, (h) adminForums.php, (i) adminPolls.php, (j) adminSmileys.php, (k) poll.php, and (l) move.php. CVE-2006-3339  Publish Date: 7/3/2006   secure/ConfigureReleaseNote.jspa in Atlassian JIRA 3.6.2-#156 allows remote attackers to obtain sensitive information via unspecified manipulations of the projectId parameter, which displays the installation path and other system information in an error message. CVE-2006-3338  Publish Date: 7/3/2006   Cross-site scripting (XSS) vulnerability in Atlassian JIRA 3.6.2-#156 allows remote attackers to inject arbitrary web script or HTML via unspecified vectors in a direct request to secure/ConfigureReleaseNote.jspa, which are not sanitized before being returned in an error page. CVE-2006-3337(cPanel)Publish Date: 7/3/2006   CVSS Severity:4.7 (Medium) Cross-site scripting (XSS) vulnerability in frontend/x/files/select.html in cPanel 10.8.2-CURRENT 118 and earlier allows remote attackers to inject arbitrary web script or HTML via the file parameter. vulnerabilities published only last Monday

  4. A Closer Look – CVE-2006-3344 • Digital Armaments advisory is 05.02.2006 • • I. Background • The SpeedStream Wireless DSL/Cable Router is usually adopted for home and small business solutions. Together with an existing DSL or cable modem connection, this affordable, easy to use connection sharing solution brings the freedom of high-speed, wireless broadband connectivity to home and SOHO networks. Its comprehensive functionality provides vital firewall protection, IP sharing capabilities, and fundamental routing features that support popular protocols like NetMeeting and VPN. • For further information or detail about the software you can refer to the vendor's homepage: • • II. Problem Description • Speedstream routers have UPnP/1.0 support. An attacker can access protected files and bypass the password protection without login using the UPnP part of the tree. • III. Detection • This problem has been detected on latest version of Siemens Speedstrem Router. It has been tested on the Speedstream 2624. • IV. Impact analysis • Successful exploitation allow an attacker to bypass the password protection. It also allow an attacker to access protected files without login. • V. Solution • First notification 05.02.2006. • Second notification 05.20.2006. • No answer from the vendor. • VI. Credit • Jaime Blasco - jaime.blasco (at) eazel (dot) es [email concealed] is credited with this discovery.

  5. Internet • Internet as „the“ network • Based on the early 70th ARPA-network (Advanced Research Projects Agency) • Internet protocols • IP: internet protocol • ICMP: internet control message protocol • TCP: transmission control protocol • ARP: address resolution protocols

  6. TCP/IP - Model (a la ISO/OSI) FTP, SMTP, HTTP FTP, SMTP, HTTP TCP, UDP TCP, UDP IP IP Application-layer Transport-layer Reliable protocol Network-layer Packages, routing Data link-layer frames Physical-layer bitstreams

  7. IP – SecurityPrivacy If privacy is outlawed, only outlaws will have privacy Phil Zimmermann By 2010, driven by the improving capabilities of data analysis, privacy will become a meaningless concept in Western societies Gartner group

  8. Phishing • Social engineering (bank customers) • Faking web pages of bank • mismatch of real and visible URLs • Requesting PIN/TAN from customers

  9. Network Services - DNS • Domain Network Service provides translation of host names ( to IP-addresses (e.g. • DNS-server provide two data bases: • IP-addresses -> host names (reverse lookup) • Host names -> IP-addresses (lookup) • No mechanisms to secure consistency of tables! • DNS-server are distributed

  10. Pharmining - DNS-Spoofing • Faking of the reverse -lookup table • Reverse lookup (e.g. for rlogin) provides Bobs host name instead of Eve‘s for Eve‘s IP-address • Access to Alice‘s host if Bob is member of /etc/hosts.equiv or in .rhosts • Countermeasure: forward and reverse lookup • Sending faked update messages to the cache of DNS-server • Manipulating C:\windows\system32\drivers\etc\hosts

  11. Observations of Users in Networks eavesdropper staff X Switch staff X Switch Link-to-link encryption:

  12. Observation of Users in Switched Networks Link-to-link encryption End-to-end encryption of content staff X Switch Problem of traffic data: who communicates with whom, how long, where?

  13. Abilities of a Potential Attacker Worst case analysis: • Observation of all communication channels • Generation of new messages • Operating some network services (e.g. as an anonymity service, as a web server, etc) • No break of cryptographical systems • No attack on user‘s personal machine • Limited time and computing power

  14. Anonymity and Unobservability Anonymity: • Sender and/or receiver stay anonymous to each other Unobservability: • All parties cannot trace communication relations • Sending and receiving of messages is unobservable Pseudonym: • identity can only be revealed in special cases

  15. Anonymity and Unobservability Need for a group of users where all users behave similarily Events Anonymity group Everybody can be the originator of an event with equal possibility

  16. Simple Proxies • Proxy gets an URL on behalf of the user • Server has no information about the real originator of the request • Examples: • (Lance Cottrel) • • (Lucent, Bell Labs) User Server Proxy

  17. Problems with Simple Proxies • No protection against the operator • No protection against traffic analysis • Timing correlation of incoming and outgoing requests • Correlation by message length and coding http proxy User 1 GET page.html User 2 ... GET page.html User n

  18. Possible Attacks • Timing attacks: • Observe duration by linking possible endpoints of communication, wait for a correlation between events at endpoints • Message volume attacks: • Observe the amount of transmitted data • Flooding attacks: • Almost all messages except the message to be observed are created by the attacker • Linking attacks: • Observe intersections of anonymity groups due to on/off-line periods (profiles)

  19. Broadcast Message is sent to all participants But only one person is able to read it

  20. Mixes (David Chaum, 1981) • Collect messages in batches, change their coding and forward them at the same time but in different order • Use of various mixes • If one mix is not corrupt then perfect unlinkability of sender and receiver

  21. Internals of Mixes Mix Discard message repeats Store incoming messages Wait for a Sufficient Number Change coding Reorder messages Avoid replay attacks

  22. Encryption of Messages • ci encryption with public key of Mixi • Ai address of Mixi • M message to be sent • ri : random numbers (to ensure indeterminism) A1, c1(A2, c2(M, r2), r1) M A2, c2(M, r2),

  23. Real Time Aspects • Mixes are good for non-real time communication: E-mail • Problems with real-time applications like net-phone, ftp, www • Sampling messages yields high delay • Message length vary in a very large interval or no support of connection oriented services

  24. Traffic padding and Time Slices Waiting time Traffic padding Sending of random data to cover last message Traffic padding Waiting time

  25. Dummy Traffic • Users (not Mixes) send messages all the time • Nobody can distinguish between encrypted messages and faked ones (random numbers) • Increases amount of traffic if necessary • Avoiding high delay of messages

  26. Flooding and Attacks • Flooding Attacks: • Introduction of tickets to be processed by a Mix • Only one message of a user in one branch • Attacker needs help of other users • Long-time observation: • Intersection of anonymity groups • No good solution known for this attack

  27. IP – SecurityAvailability, Integrity

  28. Internet Control Message Protocol • Transfer of error- and status- messages • destination unreachable: unreachable port (host) • Forged message may cause abortion of all traffic to this hosts • fragmentation needed • Continuing generation of faked message causes denial of service • Redirect : to change routing behaviour • Rerouting of all packets of a host via a malicous host • Source quench : to reduce traffic caused by a host • faked message causes denial of service

  29. Address Resolution Protocols (ARP) • Translating IP-names (e.g. to real physical addresses (eg. 00:A0:C9:44.BA.20) inbuilt in the firmware of physical device • ARP address-table of the router • Updated via broadcast messages („Who is?“) • Masquerading: faked answers to broadcast messages • Denial-of-service: request for non-existing host is broadcasted through gateways. Malicious host may even redistribute requests coming back!

  30. TCP - Connections • Logical connections between ports • TCP-packet contains: • 32bit-addresses of sender and receiver • 32bit sequence number • Randomly generated • 3-phased handshake: • Client -> Server: Seqc • Server -> Client: SeqS, Ack = Seqc + 1 • Client -> Server: Ack = SeqS + 1 • Client -> Server: Data

  31. Security in TCP - Sequence numbers • Masquerading using sequence number attacks: • To incorporate a malicious packet into an ongoing communication the intruder has to know the sequent number • Implementations use 32bit counter to generate sequence number (instead random numbers)(counter is incremented every second by 1, new connections will increment counter by 64) • Sequence numbers can be guessed

  32. Security in TCP - Sequence numbers • Eve -> Alice: Port 25, SeqEve • Alice -> Eve: Ack: SeqEve + 1, SeqAlice Guessing seqAlice‘ : • Eve as Bob -> Alice: Port 513, SeqEve‘ • Alice -> Bob: Ack: SeqEve‘ + 1, SeqAlice‘ • Eve as Bob -> Alice: Ack: SeqAlice‘ + 1 Problem: answers of Bob are sent to Alice: Additional attack neccessary to flood Alice with requests to prevent Alice from sending reset- packets

  33. Security Problems in IP: Denial of Service Address spoofing – Examples of denial of service: • UDP-flood attack: • Eve sends UDP-packet with faked return-address • Target machine sends echo-packets to machine of return address which echos etc... • SYN-flood attack: • Eve sends SYN-packets with faked return addresses of non-available machines • Target sends SYN-Ack packets • Overflow of SYN-stack

  34. Distributed Denial of Service Attacker Stepping stones Handler Agent Attack Attack Attack

  35. Intrusion Detection Systems Intrusion Detection is the process of identifying and responding to malicious activity targeted at computing and network resources Edward Amoroso

  36. Intrusion Detection Systems • Monitoring: • Examine and process information about activities on the target system • Reporting: • Report information about monitored system into a system security infrastructure • Responding: • Respond to detected intrusion

  37. Dimensions of IDS • Analysis approach: • Attack signature detection identifies patterns corresponding to known attack • Types of attacks have to be known in advance • Anomaly detection: • Identifies unacceptable deviation form expected behaviour using profiles • Can respond to previously unknown types of attacks

  38. Methods of IDS • Audit trail processing: • Existing log-files are examined by IDS • Off-line • Auditable events, auditable information, audit basis • Example: Unix Syslog Audit Processing • On-the-fly processing („network intrusion detection“) • Monitoring of traffic in real-time • Suspicious string patterns „/etc/passwd“ • Signatures of abnormal behaviours • Warnings before damage can occur

  39. Methods of IDS (II) Anomality Detection • Profiles of normal behaviour Capturing expectations about user and system computing and networking activities • Estimation of initial profile • Fine-tuning of profiles • Profiling using all-source information

  40. Architecture of an IDS • Sensor: Provides necessary information about target • System management: maintain control over internal components, communication with over IDS • Processing engine: reduction of irrelevant data, identification of key intrusion evidence, decision-making of type of response • Knowledge base: profiles of user and data, attack signatures • Audit archive: storage of target system activities • Alarms • GUI

  41. Intrusion Response • Identification of the attacker • DNS ??? • Identification of intermediate hosts • Preventing damages • Closing ports and network connections • Counter attack by denial of service attack ??? • Repair of existing damages • Loss of integrity, accessability, authentication, privacy?

  42. Firewalls Intranet • All traffic between intranet and open network is controlled by the firewall • Security strategy, access control, protocols, authentication Open network (Internet) Firewall e.g. router

  43. Types of Firewalls • Packet filter • Controlling IP (TCP) packets • Circuit-level gateway • Operates on transport layer • Application-level gateway (proxy server) • Operates on application layer • Can analyse application data

  44. Packet Filters Rules: sender receiv. port proto. action reason * * 53 UDP ok DNS-queries Extern intern 123 UDP ok NTP-access * * 69 UDP no no TFTP Extern * 513 TCP no no rlogin from outside • Filters packets (TCP / IP) according to a security policy based on header information • No internal state • Accessable information: • Sender/receiver addresses, ports, options, ack-bit, type of protocol, ...

  45. Packet Filters - Pros and Cons • Easy and cheap to implement • Transparent for upper layers • Prevents some IP-spoofing and router attacks But: • Uses possibly faked IP-addresses and ports • No detailed filtering (e.g. according to users) • Error-pruned specification of filter table • Large, unreadable tables • Need for tools

  46. Circuit-level Gateway • Controls the transport layer • Operates as client for the server and as server for the client (proxy - server) • Provides generic proxy services • Has internal state and protocols activities • Example: SOCKS - gateway (Hummingbird) • Provides socket access via rconnect, rlisten and rbind through gateway with authentication

  47. Circuit-Layer Gateway - Pros and Cons • Independent of applications • Allows for filtering of existing connections • Authorization and logging • Filtering of UDP services possible But: • Do not consider application specific information • Cannot distinguish http-content • Modification of application necessary

  48. Application Filter • Operating on application layer • Proxies for telnet, ftp, smtp, http, ... • Provides application specific knowledge • E.g. ftp-proxy knows about ftp-commands • http-proxy about activeX, Javascript, JAVA... • Internal state and logging

  49. Application Filter - Pros and Cons • Allows for sophisticated authentication and controlling (e.g. generating profiles) • Accounting and logging of accesses • Intrusion Detection Systems • Fine granular rules possible But: • Individual fiter for each service - Automation ? • Based on unreliable lower layers

  50. Architecture of Firewalls NTP-server Intranet Internet Application filter Packet filter Intranet Packet filter Application filter Dual-Home Bastion Internet Dual-Home Firewall Screened-Host Firewall