Hostmasks

Hostmasks are a concept used on some Internet Relay Chat (IRC) networks to identify or match a connected user. The most common form is the string nickname!ident@host, where the nickname represents the user’s chosen display name, ident is the user name, and host identifies the connection’s source. In practice, servers may treat the host portion as a mask that can be checked against patterns for moderation and access control.

Structure and patterns vary, but the idea is to allow flexible matching. A full hostmask might look like [email protected]. For moderation and bans, operators frequently use wildcard-based masks such as *!*@*.example.com to ban all users from a domain, or *!*@123.45.67.* to cover an IP range. Wildcards * and ? are commonly supported to match multiple possibilities. Some networks also allow masking just the host part, such as *!*@host.example.com, to apply rules regardless of nickname or ident.

Usage and purposes include moderation, access control, and tracking. Hostmasks enable operators to ban or grant privileges to groups of users based on their source, not just their visible nickname. They are also used in conjunction with services that manage accounts (for example, nick services) to tie a user’s identity to a registered handle. Users can see their hostmask via WHO or similar commands, depending on the network’s configuration.

Limitations and privacy considerations are important. Hostmasks can reveal the user’s network, and many users connect through proxies, VPNs, or dynamic IPs, which can change frequently. Because masks can be spoofed or circumvented, hostmasks are not a foolproof method of identification but remain a practical tool for network administration and moderation.