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Types of floods

Crapflood

This is the simplest type of IRC flooding. It involves posting large amounts of posts or one very long post with repetitive text. It can also involve text with no meaning or no pertinence to the current discussion.^[1] This type of flood is most commonly achieved by copying and pasting one short word repeatedly. Occasionally, when there are a large amount of small words, the entire message will be copied and pasted to produce massive amounts of text. This can, in turn, be done again, creating an exponential rise in the amount of text.

CTCP flood

Since CTCP is implemented in almost every client^{[citation needed]}, most users respond to CTCP requests. By sending too many requests, after a couple of answers they get disconnected from the IRC server. The most widely-used type is CTCP PING, although most clients also implement other CTCP replies.

DCC flood

Initiating many DCC requests simultaneously. Theoretically it can also be used to disconnect users, because the target client sends information back about what port is intended to be used during the DCC session.

ICMP flood

Typically referred to as a ping flood. This attack overloads the victim's internet connection with an amount of ICMP data exceeding the connection's capacity, potentially causing a disconnection from the IRC network. For the duration of the attack, the user's internet connection remains hindered. Technically speaking, this is not an IRC flood, as the attack itself doesn't traverse the IRC network at all, but operates entirely independent of anything but the raw internet connection and its IP protocol (of which ICMP is a subset). Even so, the actual IP address to flood (the address of the victim's connection) is frequently obtained by looking at the victim's user information (e.g. through the /whois or /dns command) on the IRC network.

Message flood

Sending lots of private messages to the victim, mainly from different connections called clones (see below). Since some clients separate the private conversations into another window, each new message could open a new window for every new user a message is received from. This is exploitable by sending messages from multiple names, causing the target client to open many new windows and potentially swamping the user with boxes. Sometimes the easiest way to close all the windows is to restart the IRC client, although scripts (client extensions) exist to 'validate' unknown nicknames before receiving messages from them.

Notice flood

Similar to the message, but uses the "notice" command.

Invite flood

Sending lot of invites.

Nick flood

Changing the nick as fast as possible, thus making the conversation unenjoyable in the channel.

Connect flood

Connecting and disconnecting from a channel as fast as possible, therefore spamming the channel with dis/connect messages, thus making the conversation unenjoyable.

Clones

Abusers do not flood from their own nicknames, because of the following reasons:

• • they can easily be K-Lined by administrators ('IRCops,' 'ServerOPs' or 'SOPs'),

  • banned from channels by operators ('ChanOPs' or 'OPs'),

  • from one user the flood is often not effective (The limits apply to the attacker too).

Instead clones are used, which are script or program controlled clients, primary designed to abuse others. When this method is used, it becomes easier to attack a user using many clones at the same time. Generally, the more clones an attacker has, the greater the chance of an attack succeeding. However the maximum connections from any one ip address are generally limited by the IRC network (either at the IRCD level or the services level).

One common way to increase the number of clones is by using open proxies. Basically these proxies are SOCKS orSquid-based, which support IRC connections by default. If one has a list of open proxies, he can use them to connect his clones through them to various IRC servers. Alternatively, compromised systems can be used to make the connections.

To prevent this, nowadays some IRC servers are configured to check common proxy ports of the client at the very beginning of the connection. If a successful proxy request can be done, it immediately drops the user (or clone). Other IRC networks use a separate proxy scanner that scans users as they join the network and kills or glines any users it detects an open proxy on. However this offers no protection against compromised systems or proxies on nonstandard ports (a full 65535 port scan isn't really feasible both for performance reasons and because it risks setting off Intrusion Detection Systems).

Protection

Almost every IRC client offers some kind of flood protection. These protections are based on the built-in "ignore" feature, which means that a given incoming message, CTCP, invitation, etc. will be blocked if the sender's hostmask matches any of the masks are defined in the ignore list. This is useful as few IRC networks implement the 'silence' command to reject messages by the server. In other words, every message will be posted to the correspondent user, whether it is a normal message or its content is intentionally malicious.

Many clients also limit the number of replies that can be sent in response to any incoming traffic from the network thus avoiding hitting the excess flood limit.

Flood protection in mIRC

There's also flood protection in the popular Windows-based client program, mIRC, in the Options menu. Users can set up some important values about how many incoming bytes are considered to be flooding, maximum incoming lines per user and ignorance time. Note that these settings are not enabled by default.

Despite these possibilities, there are much more sophisticated ways to eliminate flooding using mIRC scripts. These include additional features, such as CTCP cloaking, better message flood control, more adjustable flood triggers, and many others.

Firewalls and floods

Many users believe that installing a firewall will protect them against these attacks. But firewalls typically don't deal with this kind of application layer denial-of-service attack and no known application layer firewalls provide such protection for IRC at this time.

See also

• Computer security

• WinNuke

• Smurf attack

Notes

• 1. ^ An example of this would be someone posting the entire contents of a book or poem when the book or poem in question is unrelated to discussion.

References

Example of a message flood using over 50 clones.

A post flood on #wikipedia-en, using the common Internet term "OMG".

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