Unfortunately, not all XMPP entities are well-behaved -- they may send spam of various kinds, harrass chat rooms, generate large amounts of traffic, etc. Currently, if an XMPP entity (the "attacker") sends abusive stanzas to another XMPP entity (the "victim"), there is no way for the victim or the victim's server to inform the attacker's server that the attacker is generating abusive traffic. In current practice, the victim's server may have no choice but to terminate the server-to-server connection rather than continue to accept the abusive traffic.
This situation is far from desirable. Therefore, this specification defines several protocol functions that can help to discourage abuse on the XMPP network:
An abuse report shall be sent in an IQ stanza of type "set" containing an <abuse/> element qualified by the 'urn:xmpp:tmp:abuse' namespace (see Protocol Namespaces regarding issuance of one or more permanent namespaces).
The children of the <abuse/> element are as follows:
This specification intentionally does not define exactly what constitutes abuse, since "abuse is in the eye of the beholder". However, the following machine-readable conditions are defined as children of the <reason/> element.
|<gateway/>||Attempting to inappropriately use a gateway on the receiving server (see Gateway Interaction (XEP-0100) )|
|<muc/>||Attempting to take over or otherwise abuse Multi-User Chat (XEP-0045)  rooms on the receiving server|
|<proxy/>||Attempting to inappropriately use a SOCKS5 Bytestreams (XEP-0065)  proxy, TURN server, or other proxy on the receiving server|
|<pubsub/>||Attempting to inappropriately use a Publish-Subscribe (XEP-0060)  service on the receiving server|
|<service/>||Attempting to inappropriately use any other kind of service on the receiving server|
|<spam/>||Sending spam (unsolicited bulk messages)|
|<stanza-too-big/>||Sending extremely large stanzas|
|<too-many-recipients/>||Sending messages that contain too many recipients (see Extended Stanza Addressing (XEP-0033) )|
|<too-many-stanzas/>||Sending an extremely large number of stanzas|
|<unacceptable-payload/>||Sending messages that contain unacceptable payloads such as malicious executables|
|<unacceptable-text/>||Sending messages that contain unacceptable human-readable text|
|<undefined-abuse/>||The abuse condition is undefined (should be used with an application-specific condition)|
Note: The foregoing list of conditions is not exhaustive. The list may be augmented or otherwise modified in a future version of this specification as a result of implementation and deployment experience.
An abuse report can be generated by the victim or the victim's server. If the report is generated by the victim's server, the report MUST be sent to the attacker's server. If the report is generated by the victim, the report MUST be sent to the attacker's server and SHOULD also be sent to the victim's server as well (since the victim may not know if the attacker's server is a rogue server).
The following rules and guidelines apply to the act of reporting abuse.
The recipient SHOULD NOT report the abuse stanza to a server or service until it determines that the server or service supports the Abuse Reporting protocol (see the Discovering Support section of this document).
The recipient SHOULD report the abuse to the suspected abuser's server.
If the recipient's home server (i.e., the server with which it has a registered account or other trust relationship) supports the abuse Reporting protocol, the recipient SHOULD also report the offending stanza to its own server.
If the recipient's home server does not support the Abuse Reporting protocol, the recipient SHOULD report the abuse stanza to one or more dedicated abuse reporting services if available.
The recipient SHOULD NOT report the abuse stanza to the suspected abuser.
Upon receiving the abuse report, the attacker's server MUST proceed as follows.
If the sending server does not understand the abuse reporting protocol, it MUST return a <service-unavailable/> error.
If the JID contained in the abuse report does not exist at the attacker's server, it MUST return an <item-not-found/> error.
Otherwise, if the sending server accepts the abuse report, it MUST return an IQ stanza of type "result".
This specification does not define how a sending server shall behave when it receives an abuse report. In general it is expected that the sending server (1) will notify the human administrators of the server in some implementation-specific or deployment-specific fashion, and (2) may employ the abuse report in an automated fashion (e.g., as input to a rate-limiting algorithm, reputation system, or decision about temporarily suspending the privileges of the sending entity based on JabberID or IP address).
The following rules and guidelines apply to the processing of an abuse report:
Not all abuse reports are valid, and not all JIDs that send stanzas reported as abuse are abusers. Care must be taken in correctly determining if a suspected abuser is an actual abuser. The following rules apply:
The processor SHOULD NOT add a suspected abuser to its list of known abusers until it has received at least three (3) valid abuse reports with regard to that suspected abuser, or until it has independently verified the veracity of the report.
If the processor determines that the suspected abuser is an actual abuser, the processor:
If the attacker's server determines that the suspected attacker is an actual attacker, it might decide that both the JabberID and the IP address associated with the attacker's JabberID are compromised. If it does so, it SHOULD report its conclusions to appropriate other entities (e.g., trusted peer servers or dedicated abuse reporting services). The protocol is quite simple: include the JabberID and IP address as children of an <abuser/> element qualified by the 'urn:xmpp:tmp:abuse' namespace and send an IQ stanza of type "set" to the entity that shall receive the report. This protocol SHOULD NOT be used directly by victims of abusive stanzas and if an entity receives such a report from an end user it SHOULD ignore it. The following is an example:
If the victim's server determines that the attacker's server is a bad actor on the network (i.e., a rogue server), it SHOULD report its conclusions to appropriate other entities (e.g., trusted peer servers or dedicated abuse reporting services). This is done by including the domain name (and optionally IP address) of the rogue server in a <rogue/> element qualified by the 'urn:xmpp:tmp:abuse' namespace and send an IQ stanza of type "set" to the entity that shall receive the report. This protocol SHOULD NOT be used directly by victims of abusive stanzas and if an entity receives such a report from an end user it SHOULD ignore it. The following is an example:
The receiving server MAY report that a particular stanza is considered abusive. The stanza error condition MUST be <not-acceptable/> and the error stanza MUST include an application-specific error condition of <abuse/> qualified by the 'urn:xmpp:tmp:abuse' (see Protocol Namespaces regarding issuance of one or more permanent namespaces). The <abuse/> element MUST include one or more <jid/> elements whose XML character data specifies the JID(s) of the abusive sender(s).
If the sending entity continues to generate abusive stanzas via the sending server, the receiving server MAY close the stream between the receiving server and the sending server. The stream error condition MUST be <policy-violation/> and the stream error MUST include an application-specific error condition of <abuse/> qualified by the 'urn:xmpp:tmp:abuse'. The <abuse/> element MUST include one or more <jid/> elements whose XML character data specifies the JID(s) of the abusive sender(s).
The receiving entity then SHOULD terminate the TCP connection between the receiving server and the sending server.
If a server supports the abuse reporting protocol, it MUST report that fact by including a service discovery feature of "urn:xmpp:tmp:abuse" (see Protocol Namespaces regarding issuance of one or more permanent namespaces) in response to a Service Discovery (XEP-0030)  information request:
Not all reported abuse is actual abuse, and not all reported abusers are actual abusers. Processors must take care to ensure that processing of one or a few reports does not result in branding of a legitimate sender as an abuser, since otherwise the sender could effectively be the subject of a denial of service attack.
It is NOT RECOMMENDED for victims to send abuse reports to the server of a suspected abuser, since that server could be a rogue domain capable of sending abuse from any JID at that domain.
It is possible for an abusive sender to launch a denial of service attack against legitimate users of the sending server by generating abusive traffic over the server-to-server connection (in fact such attacks have already been observed on XMPP networks). Although use of the abuse reporting protocol does not completely prevent such attacks, it may at least enable sending servers to react to abusive traffic in close to real time, thus helping to "heal" the network when denial of service attacks are launched.
If a malicious entity can inject information into the server-to-server connection, it can falsely send abuse reports to the sending server. Therefore the connection SHOULD be encrypted using Transport Layer Security as specified in XMPP Core .
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) .
Until this specification advances to a status of Draft, its associated namespace shall be "urn:xmpp:tmp:abuse"; upon advancement of this specification, the XMPP Registrar  shall issue a permanent namespace in accordance with the process defined in Section 4 of XMPP Registrar Function (XEP-0053) .
The XMPP Registrar shall add <abuse/> to its registry of application-specific error conditions (see <https://xmpp.org/registrar/errors.html>), where the element is qualified by the 'urn:xmpp:tmp:abuse' namespace (see Protocol Namespaces regarding issuance of one or more permanent namespaces).
The registry submission is as follows:
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Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/
Generalized text and protocol to handle all kinds of abuse and folded in content from XEP-0236.
Specified that client recipient should not send a report to the server of a suspected abuser; modified XML namespace name to conform to XEP-0053 processes; corrected several examples.
Modified business rules; added security considerations; defined XML schema.