able to define the range of addresses, protocols, and ports for deception. The process involves a router passing the supported traffic to the appropriate server while those sent by other contacts are sent to the tarpit. Examples of tarpits include the Labrea tarpit, Honeyd, SMTP tarpits, and IP-level tarpits. Collateral damage Measures to protect against spam can cause collateral damage. This includes: The measures may consume resources, both in the server and on the network. When a mail server rejects legitimate messages, the sender needs to contact the recipient out of channel. When legitimate messages are relegated to a spam folder, the sender is not notified of this. If a recipient periodically checks his spam folder, that will cost him time and if there is a lot of spam it is easy to overlook the few legitimate messages. Measures that imposes costs on a third party server may be considered to be abuse and result in deliverability problems. Automated techniques for email senders There are a variety of techniques that email senders use to try to make sure that they do not send spam. Failure to control the amount of spam sent, as judged by email receivers, can often cause even legitimate email to be blocked and for the sender to be put on DNSBLs. Background checks on new users and customers Since spammer's accounts are frequently disabled due to violations of abuse policies, they are constantly trying to create new accounts. Due to the damage done to an ISP's reputation when it is the source of spam, many ISPs and web email providers use CAPTCHAs on new accounts to verify that it is a real human registering the account, and not an automated spamming system. They can also verify that credit cards are not stolen before accepting new customers, check the Spamhaus Project ROKSO list, and do other background checks. Confirmed opt-in for mailing lists A malicious person can easily attempt to subscribe another user to a mailing list — to harass them, or to make the company or organisation appear to be spamming. To prevent this, all modern mailing list management programs (such as GNU Mailman, LISTSERV, Majordomo, and qmail's ezmlm) support "confirmed opt-in" by default. Whenever an email address is presented for subscription to the list, the software will send a confirmation message to that address. The confirmation message contains no advertising content, so it is not