As XMPP technologies have been deployed more widely, the open XMPP network has become a more significant target for attacks. This specification defines ways for XMPP server deployments to share information with each other and therefore to handle such attacks in a more real-time fashion. In particular, it defines a way to use the IODEF format (defined in &rfc5070; and produced by the IETF's INCH Working Group) as the basis for sharing incident reports among XMPP server deployments. (For some related considerations, see &rfc2350; and &rfc3067;.)

This document defines several interactions (similar to those in RID, see &rfc6045;) between XMPP server deployments with respect to incident handling. These interactions are transported using the XMPP &IQ; stanza as described below, where each element (qualified by the 'urn:xmpp:incident:2' namespace) is used as a wrapper for IODEF data.

1. The <report/> element (contained in an &IQ; stanza of type "set") describes the nature of an incident and also flags the 'status' of the incident as "new", "updated", or "resolved"; it is sent from one server to another for informative purposes but without requesting assistance (for which see the <request/> element). This element is similar to a RID message type of "Report".

2. The <inquiry/> element (contained in an &IQ; stanza of type "get") asks for information about an incident; it is expected that the reply will contain a <report/> element. This element is similar to a RID message type of "IncidentQuery".

3. The <request/> element (contained in an &IQ; stanza of type "get") asks for assistance in resolving an incident, e.g., by requesting that the server take some action. This element is similar to a RID message type of "Investigation" or "TraceRequest".

4. The <response/> element (contained in an &IQ; stanza of type "set") provides assistance in resolving an incident. This element is similar to a RID message type of "Result".

When one server wants to send information about an incident, it sends a incident report to another server. The report consists of an XMPP &IQ; stanza of type "set" containing a <report/> element that in turn contains an IODEF document. An example is shown below.

If the recipient is able to process the report, it MUST return an &IQ; stanza of type "result"; if not, it MUST return an &IQ; stanza of type "error" (error handling will be defined in a future version of this specification).

When one server wants to find out more information about an incident, it sends an inquiry to another server (not necessarily the server where the incident occurred).

If the recipient is able to process the inquiry, it MUST return an &IQ; stanza of type "result" and then send a report about the incident using an &IQ; stanza of type "set" as defined above; if not, it MUST return an &IQ; stanza of type "error" (error handling will be defined in a future version of this specification).

When one server wants to ask for assistance in resolving an incident, it sends a request to another server (not necessarily the server where the incident occurred).

Here, the server where the attack occurred requests that the server where the attack originated will disable the offending accounts (via the "block-host" value for the 'action' attribute of the IODEF <Expectation/> element).

If the recipient is able to process the report, it MUST return an &IQ; stanza of type "result"; if not, it MUST return an &IQ; stanza of type "error" (error handling will be defined in a future version of this specification).

When one server provides assistance in resolving an incident, it sends a response to another server (not necessarily the server where the incident occurred).

Here, the server where the attack originated informs the server where the attack occurred that it has disabled the offending accounts (via the IODEF <HistoryItem/> element).

If the recipient is able to process the report, it MUST return an &IQ; stanza of type "result"; if not, it MUST return an &IQ; stanza of type "error" (error handling will be defined in a future version of this specification).

This document defines the following IODEF extensions, described in accordance with the guidelines in &miletemplate;.

The &JID; element qualified by the 'urn:xmpp:incident:2' namespace is a "JID slot" as described in &rfc6122bis;.

Note: Definition of the &JID; element might be moved to a separate specification.

It is RECOMMENDED for a server deployment to exchange incident reports only with peer servers that it trusts, for example peers that are in its "server roster" as described in &xep0267;.

This technology is designed to help mitigate attacks on the XMPP network. However, incident reporting is itself vulnerable to the following attacks:

• False reports could lead a server to deny service to legitimate users or peer servers (see also &xep0205;). To help mitigate such attacks, a server SHOULD treat with caution any incident reports that it might receive from untrusted entities.
• If traffic between two servers is not protected using Transport Layer Security (TLS), a passive eavesdropper could gain access to incident reports and therefore adjust its behavior in response. To prevent such attacks, servers SHOULD use TLS.

Use of the XMPP channel is convenient for communication among XMPP servers; however, if a denial of service attack is severe enough then that channel itself might be unusable.

Unless explicitly configured to do so, a receiving server SHOULD NOT automatically modify its configuration based on receipt of an incident report, even from a trusted server, but instead SHOULD prompt the human administrators so that they can take appropriate action.

A receiving server MAY accept incident reports from peers that are not on its "trust list", but SHOULD treat such reports with caution and provide them to the human administrator(s) of the server.

A receiving server MAY forward reports that it receives to other servers it trusts.

This document might require interaction with &IANA; to register various IODEF extensions, in accordance with draft-ietf-mile-template.