This article is about analysis of traffic in a radio or computer network. For vehicular traffic, seeTraffic flow.
Traffic analysis is the process of intercepting and examining messages in order to deduce information from patterns incommunication. It can be performed even when the messages areencrypted.[1] In general, the greater the number of messages observed, the greater information be inferred. Traffic analysis can be performed in the context ofmilitary intelligence,counter-intelligence, orpattern-of-life analysis, and is also a concern incomputer security.
Traffic analysis tasks may be supported by dedicated computersoftware programs. Advanced traffic analysis techniques which may include various forms ofsocial network analysis.
Traffic analysis has historically been a vital technique incryptanalysis, especially when the attempted crack depends on successfully seeding aknown-plaintext attack, which often requires an inspired guess based on how specific the operational context might likely influence what an adversary communicates, which may be sufficient to establish a short crib.
Traffic analysis method can be used to break theanonymity of anonymous networks, e.g.,TORs.[1] There are two methods of traffic-analysis attack, passive and active.
In passive traffic-analysis method, the attacker extracts features from the traffic of a specific flow on one side of the network and looks for those features on the other side of the network.
In active traffic-analysis method, the attacker alters the timings of the packets of a flow according to a specific pattern and looks for that pattern on the other side of the network; therefore, the attacker can link the flows in one side to the other side of the network and break the anonymity of it. It is shown, although timing noise is added to the packets, there are active traffic analysis methods robust against such a noise.[failed verification][1]
In a military context, traffic analysis is a basic part ofsignals intelligence, and can be a source of information about the intentions and actions of the target. Representative patterns include:
Frequent communications – can denote planning
Rapid, short communications – can denote negotiations
A lack of communication – can indicate a lack of activity, or completion of a finalized plan
Frequent communication to specific stations from a central station – can highlight thechain of command
Who talks to whom – can indicate which stations are 'in charge' or the 'control station' of a particular network. This further implies something about the personnel associated with each station
Who talks when – can indicate which stations are active in connection with events, which implies something about the information being passed and perhaps something about the personnel/access of those associated with some stations
Who changes from station to station, or medium to medium – can indicate movement, fear of interception
There is a close relationship between traffic analysis andcryptanalysis (commonly calledcodebreaking).Callsigns and addresses are frequentlyencrypted, 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 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:
TheCommunications' Metadata Intelligence, orCOMINT metadata is a term incommunications intelligence (COMINT) referring to the concept of producing intelligence by analyzing only the technicalmetadata, hence, is a great practical example for traffic analysis in intelligence.[2]
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.
For example, if an emitter is known as the radio transmitter of a certain unit, and by usingdirection finding (DF) tools, the position of the emitter is locatable, the change of locations from one point to another can be deduced, without listening to any orders or reports. If one unit reports back to a command on a certain pattern, and another unit reports on the same pattern to the same command, the two units are probably related. That conclusion is based on themetadata of the two units' transmissions, not on the content of their transmissions.
Using all or as much of the metadata available is commonly used to build up anElectronic Order of Battle (EOB) by 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, which, alongside tapping, builds a much better and complete picture.
British analysts duringWorld War I noticed that thecall sign of German Vice AdmiralReinhard Scheer, commanding the hostile fleet, had been transferred to a land station.Admiral of the FleetBeatty, ignorant of Scheer's practice of changing call signs upon leaving harbour, dismissed its importance and disregardedRoom 40 analysts' attempts to make the point. The German fleet sortied, and the British were late in meeting them at theBattle of Jutland.[3] If traffic analysis had been taken more seriously, the British might have done better than a "draw".[original research?]
French military intelligence, shaped byAuguste Kerckhoffs's legacy, had erected a network of intercept stations at the Western Front in pre-war times. When the Germans crossed the frontier, the French worked out crude means for direction-finding based on intercepted signal intensity. The recording of call signs and of traffic volumes further enabled the French to identify German combat groups and to distinguish fast-moving cavalry from slower infantry.[3]
In the early part ofWorld War II, theaircraft carrierHMS Glorious was evacuating pilots and planes fromNorway. Traffic analysis produced indicationsScharnhorst andGneisenau were moving into theNorth Sea, but the Admiralty dismissed the report as unproven. The captain ofGlorious did not keep sufficient lookout and was subsequently surprised and sunk.Harry Hinsley, the youngBletchley Park liaison to the Admiralty, later said that his reports from the traffic analysts were taken much more seriously thereafter.[4]
During the planning and rehearsal for theattack on Pearl Harbor, very little traffic was passed by radio, subject to interception. The ships, units, and commands involved were all in Japan and in touch by phone, courier, signal lamp, or even flag. None of that traffic was intercepted, and could not be analyzed.[3]
The espionage effort against Pearl Harbor before December did not send an unusual number of messages; Japanese vessels regularly called in Hawaii and messages were carried aboard by consular personnel. At least one such vessel carried some Japanese Navy Intelligence officers. Such messages could not be analyzed. It has been suggested,[5] however, the volume of diplomatic traffic to and from certainconsular stations might have indicated places of interest to Japan, which might thus have suggested locations to concentrate traffic analysis and decryption efforts.[citation needed]
Admiral Nagumo's Pearl Harbor Attack Force sailed under radio silence, with its radios physically locked down. It is unclear if that deceived the US since Pacific Fleet intelligence had been unable to locate the Japanese carriers in the days immediately preceding theattack on Pearl Harbor.[3]
TheJapanese Navy played radio games to inhibit traffic analysis (see Examples, below) with the attack force after it sailed in late November. Radio operators normally assigned to carriers, with a characteristic Morse Code "fist", transmitted from inland Japanese waters, suggesting the carriers were still near Japan.[3][6]
Operation Quicksilver, part of the British deception plan for theInvasion of Normandy during World War II fed German intelligence a combination of true and false information about troop deployments in Britain, which caused the Germans to deduce an order of battle that suggested an invasion at thePas-de-Calais, instead of Normandy. The fictitious divisions that were created for the deception were supplied with real radio units, which maintained a flow of messages that was consistent with the deception.[7]
Traffic analysis is also a concern incomputer security. An attacker can gain important information by monitoring the frequency and timing of network packets. A timing attack on theSSH protocol can use timing information to deduce information aboutpasswords since, during interactive session, SSH transmits each keystroke as a message.[8] The time between keystroke messages can be studied usinghidden Markov models. Song,et al. claim that it can recover the password fifty times faster than abrute force attack.
Onion routing systems are used to gain anonymity. Traffic analysis can be used to attack anonymous communication systems like theTor anonymity network. Adam Back, Ulf Möeller and Anton Stiglic present traffic analysis attacks against anonymity providing systems.[9]Steven J. Murdoch andGeorge Danezis from University of Cambridge presented[10] 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.
Traffic analysis involves intercepting and scrutinizing cybersecurity threats to gather valuable insights about anonymous data flowing through theexit node. By using technique rooted indark web crawling and specializing software, one can identify the specific characteristics of a client's network traffic within the dark web.[11]
It is difficult to defeat traffic analysis without both encrypting messages and masking the channel. When no actual messages are being sent, the channel can bemasked[12] by sending dummy traffic, similar to the encrypted traffic, thereby keeping bandwidth usage constant.[13] "It is very hard to hide information about the size or timing of messages. The known solutions requireAlice to send a continuous stream of messages at the maximumbandwidth 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.
