词条 | Traffic analysis |
释义 |
Traffic analysis is the process of intercepting and examining messages in order to deduce information from patterns in communication, which can be performed even when the messages are encrypted.[1] In general, the greater the number of messages observed, or even intercepted and stored, the more can be inferred from the traffic. Traffic analysis can be performed in the context of military intelligence, counter-intelligence, or pattern-of-life analysis, and is a concern in computer security. Traffic analysis tasks may be supported by dedicated computer software programs. Advanced traffic analysis techniques may include various forms of social network analysis. Breaking the anonymity of networksTraffic analysis method can be used to break the anonymity of anonymous networks, e.g., TORs [1]. There are two methods of traffic-analysis attack, passive and active.
In military intelligenceIn a military context, traffic analysis is a basic part of signals intelligence, and can be a source of information about the intentions and actions of the target. Representative patterns include:
There is a close relationship between traffic analysis and cryptanalysis (commonly called codebreaking). Callsigns and addresses are frequently encrypted, requiring assistance in identifying them. Traffic volume can often be a sign of an addressee's importance, giving hints to pending objectives or movements to cryptanalysts. Traffic flow securityTraffic-flow security is the use of measures that conceal the presence and properties of valid messages on a network to prevent traffic analysis. This can be done by operational procedures or by the protection resulting from features inherent in some cryptographic equipment. Techniques used include:
Traffic-flow security is one aspect of communications security. COMINT metadata analysis{{multiple issues|section=y|{{Tone|section|date=November 2011}}{{Unreferenced section|date=November 2011}}}}The Communications' Metadata Intelligence, or COMINT metadata is a term in communications intelligence (COMINT) referring to the concept of producing intelligence by analyzing only the technical metadata, hence, is a great practical example for traffic analysis in intelligence. While traditionally information gathering in COMINT is derived from intercepting transmissions, tapping the target's communications and monitoring the content of conversations, the metadata intelligence is not based on content but on technical communicational data. Non-content COMINT is usually used to deduce information about the user of a certain transmitter, such as locations, contacts, activity volume, routine and its exceptions. ExamplesFor example, if a certain emitter is known as the radio transmitter of a certain unit, and by using direction finding (DF) tools, the position of the emitter is locatable; hence the changes of locations can be monitored. That way we're able to understand that this certain unit is moving from one point to another, without listening to any orders or reports. If we know that this unit reports back to a command on a certain pattern, and we know that another unit reports on the same pattern to the same command, then the two units are probably related, and that conclusion is based on the metadata of the two units' transmissions, and not on the content of their transmissions. Using all, or as much of the metadata available is commonly used to build up an Electronic Order of Battle (EOB) – mapping different entities in the battlefield and their connections. Of course the EOB could be built by tapping all the conversations and trying to understand which unit is where, but using the metadata with an automatic analysis tool enables a much faster and accurate EOB build-up that alongside tapping builds a much better and complete picture. World War I
World War II
In computer securityTraffic analysis is also a concern in computer security. An attacker can gain important information by monitoring the frequency and timing of network packets. A timing attack on the SSH protocol can use timing information to deduce information about passwords since, during interactive session, SSH transmits each keystroke as a message.[7] The time between keystroke messages can be studied using hidden Markov models. Song, et al. claim that it can recover the password fifty times faster than a brute force attack. Onion routing systems are used to gain anonymity. Traffic analysis can be used to attack anonymous communication systems like the Tor anonymity network. Adam Back, Ulf Möeller and Anton Stiglic present traffic analysis attacks against anonymity providing systems .[8] Steven J. Murdoch and George Danezis from University of Cambridge presented [9]research showing that traffic-analysis allows adversaries to infer which nodes relay the anonymous streams. This reduces the anonymity provided by Tor. They have shown that otherwise unrelated streams can be linked back to the same initiator. Remailer systems can also be attacked via traffic analysis. If a message is observed going to a remailing server, and an identical-length (if now anonymized) message is seen exiting the server soon after, a traffic analyst may be able to (automatically) connect the sender with the ultimate receiver. Variations of remailer operations exist that can make traffic analysis less effective. CountermeasuresIt is difficult to defeat traffic analysis without both encrypting messages and masking the channel. When no actual messages are being sent, the channel can be masked [10] by sending dummy traffic, similar to the encrypted traffic, thereby keeping bandwidth usage constant .[11] "It is very hard to hide information about the size or timing of messages. The known solutions require Alice to send a continuous stream of messages at the maximum bandwidth she will ever use...This might be acceptable for military applications, but it is not for most civilian applications." The military-versus-civilian problems applies in situations where the user is charged for the volume of information sent. Even for Internet access, where there is not a per-packet charge, ISPs make statistical assumption that connections from user sites will not be busy 100% of the time. The user cannot simply increase the bandwidth of the link, since masking would fill that as well. If masking, which often can be built into end-to-end encryptors, becomes common practice, ISPs will have to change their traffic assumptions. See also
References1. ^1 2 {{cite arxiv|last=Soltani|first=Ramin|last2=Goeckel|first2=Dennis|last3=Towsley|first3=Don|last4=Houmansadr|first4=Amir|date=2017-11-27|title=Towards Provably Invisible Network Flow Fingerprints|eprint=1711.10079|class=cs.NI}} 2. ^1 2 {{cite book | title = The Codebreakers: The Story of Secret Writing | author = Kahn, David | year = 1974 | id = Kahn-1974 | publisher = Macmillan | isbn = 0-02-560460-0 }} 3. ^{{cite web |url = http://www.warship.org/no11994.htm |title = The Loss of HMS Glorious: An Analysis of the Action |author = Howland, Vernon W. |date = 2007-10-01 |accessdate = 2007-11-26 |deadurl = yes |archiveurl = https://web.archive.org/web/20010522092000/http://www.warship.org/no11994.htm |archivedate = 2001-05-22 |df = }} 4. ^{{cite book | author = Costello, John | title = Days of Infamy: Macarthur, Roosevelt, Churchill-The Shocking Truth Revealed : How Their Secret Deals and Strategic Blunders Caused Disasters at Pear Harbor and the Philippines | publisher = Pocket | year = 1995 | isbn = 0-671-76986-3}} 5. ^{{cite book | title = "And I Was There": Pearl Harbor And Midway -- Breaking the Secrets. | author = Layton, Edwin T. |author2=Roger Pineau, John Costello | publisher = William Morrow & Co | year = 1985 | isbn =0-688-04883-8}} 6. ^{{cite book |last=Masterman |first=John C |authorlink=John Cecil Masterman |title=The Double-Cross System in the War of 1939 to 1945 |publisher=Australian National University Press |isbn=978-0-7081-0459-0 |year=1972 |origyear=1945|page=233 }} 7. ^{{Cite journal |last1=Song |first1=Dawn Xiaodong |last2=Wagner |first2=David |last3=Tian |first3=Xuqing |title=Timing Analysis of Keystrokes and Timing Attacks on SSH |publisher=10th USENIX Security Symposium |year=2001 |ref=harv |postscript=}} 8. ^{{cite web | author = Adam Back |author2=Ulf Möeller and Anton Stiglic | url = http://www.cypherspace.org/adam/pubs/traffic.pdf | title = Traffic Analysis Attacks and Trade-Offs in Anonymity Providing systems | year = 2001 | publisher = Springer Proceedings - 4th International Workshop Information Hiding}} 9. ^{{cite web | author = Murdoch, Steven J. |author2=George Danezis | url = http://www.cl.cam.ac.uk/users/sjm217/papers/oakland05torta.pdf | title = Low-Cost Traffic Analysis of Tor | year = 2005}} 10. ^{{cite web |url = http://students.cs.tamu.edu/xinwenfu/paper/ICCNMC03_Fu.pdf |title = Active Traffic Analysis Attacks and Countermeasures |author = Xinwen Fu, Bryan Graham, Riccardo Bettati and Wei Zhao |accessdate = 2007-11-06 |deadurl = yes |archiveurl = https://web.archive.org/web/20060913152709/http://students.cs.tamu.edu/xinwenfu/paper/ICCNMC03_Fu.pdf |archivedate = 2006-09-13 |df = }} 11. ^{{cite book |author1=Niels Ferguson |author2=Bruce Schneier |lastauthoramp=yes | title = Practical Cryptography | publisher = John Wiley & Sons | year = 2003 }}
Further reading
5 : Cryptographic attacks|Intelligence analysis|Military communications|Telecommunications|Computer security |
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