| Internet-Draft | MITM | December 2024 |
| Richardson & Hoyland | Expires 16 June 2025 | [Page] |
The terms on-path attacker and MITM Attack have been used in a variety of ways, sometimes interchangeably, and sometimes meaning different things.¶
Increasingly people have become uncomfortable with the gendered term "Man" in the middle and have sought alternatives.¶
This document offers an update on terminology for network attacks, retaining some acronyms terms while redefining the expansion, and clarifying the different kinds of attacks. Consistent terminology is important in describing what kinds of attacks a particular protocol defends against, and which kinds the protocol does not.¶
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A number of terms have been used to describe attacks against networks.¶
In the [dolevyao] paper, the attacker is assumed to be able to:¶
view messages as they are transmitted¶
selectively delete messages¶
selectively insert or modify messages¶
Some authors refer to such an attacker as an "on-path" attacker [reference], or a "Man-in-the-Middle" [reference].¶
Despite a broad consensus on what is meant by a MITM attack, there is less agreement on the how to describe its variants. The term "passive attacker" has been used in many cases to describe situations where the attacker can only observe messages, but can not intercept, modify or delete any messages.¶
Another variant is the case where an eavesdropper is not on the network path between the actual correspondants, and thus cannot drop messages, they may be able to inject packets faster than the correspondants, and thus beat legitimate packets in a race.¶
As summarised, there are three broad variations of the MITM attacker:¶
The attacks are numbered in this section as no consensus on naming the attacks yet. In the diagrams below, the sender is named "Alice", and the recipient is named "Bob", as is typical in many cryptographic protocols [alicebob], as first introduced by [digisign].¶
Alice and Bob were named as expansions of "A" and "B", which would otherwise be very abstract concepts of the two end points.¶
The attacker has historically been named "Mallory", but this document proposes that the expansion be named "Meddler"¶
In this attack, the attacker is involved with the forwarding of the packets. A firewall or network router is ideally placed for this attack.¶
In this case the Meddler can:¶
In this attack, the attacker is not involved with the forwarding of the packets. The attacker receives a copy of packets that are sent along the path. This could be from, for instance, a mirror port or SPAN [span]. Alternatively, a copy of traffic may be obtained via passive (optical) tap [fibertap]. This kind of attack is often associated with Pervasive Monitoring [RFC7258].¶
In this the meddler can:¶
view all packets¶
Note that they have no way to inject new packets, and this attack may occur seconds to decades after the data was exchanged.¶
In some cases, the Meddler is be able to send messages to Bob via another route. Due to some other factor (such as shorter or higher cost routing), these messages arrive at Bob prior to the original message from Alice.¶
In that the Meddler can:¶
But the Meddler is unable to drop or modify the original packets. Bob however, may be unable to distinguish packets from Alice vs packets sent from the Meddler that purport to be from Alice.¶
To be effective or useful, this type of attack needs to occur in real time.¶
The third kind of attack is one in which the Meddler can not see any packets from Alice. This is usually what is meant by an "off-path" attack. The meddler can forge packets purporting to be from Alice, but can never see Alice's actual packets.¶
In this the Meddler can:¶
insert additional packets¶
This document introduces a set of terminology that will be used in many Security Considerations sections.¶
This document makes no IANA requests.¶
The SAAG mailing list.¶
As a special case for the MITM, if the Meddler steals cookies (whether they are HTTP Cookies, IKE nonces, or TCP SYN Cookies), then this kind of attack is a Monster in The Middle. This is otherwise known as a: nom-nom-nom-nom attack.¶