Clam AntiVirus is an anti-virus toolkit designed especially for email scanning on mail gateways. It provides a number of utilities, including a flexible and scalable multi-threaded daemon, a commandline scanner, and a tool for automatic database updates. The core of the package is an anti-virus engine available as a shared library.
John the Ripper is a fast password cracker, currently available for many flavors of Unix, Windows, DOS, BeOS, and OpenVMS. Its primary purpose is to detect weak Unix passwords. It supports several crypt(3) password hash types commonly found on Unix systems, as well as Windows LM hashes. On top of this, lots of other hashes and ciphers are added in the community-enhanced version (-jumbo), and some are added in John the Ripper Pro.
MailScanner is an email virus scanner, vulnerability protector, and spam tagger. It supports the Postfix, Sendmail, Exim, Qmail, and ZMailer MTAs, and the Sophos, McAfee, F-Prot, F-Secure, CommandAV, InoculateIT, Inoculan, eTrust, Kaspersky, Nod32, AntiVir, BitDefender, RAV, Panda, DrWeb, ClamAV, and other anti-virus scanners. It uses SpamAssassin for highly successful spam identification, and is designed to handle denial of service attacks. It will detect password-protected zip files and apply filename checking to their contents. It is very easy to install, requires no changes at all to your sendmail.cf file, is designed to be lightweight, and won't grind your mail system to a halt with its load. It can be integrated into any email system, regardless of the software in use.
HTMLDOC converts HTML files and Web pages into indexed HTML, PostScript, and PDF files suitable for online viewing and printing. It can be used as a standalone GUI application, in a batch document processing environment, as a Web-based report generation application, or in embedded environments to support printing of HTML content. It runs on all Unix platforms as well as Mac OS X and Windows 2000 and higher.
getmail is intended as a simple, secure, and reliable replacement for fetchmail. It retrieves email (either all messages, or only unread messages) from one or more POP3, SPDS, or IMAP4 servers (with or without SSL) for one or more email accounts, and reliably delivers into qmail-style Maildirs, mboxrd files, or through external MDAs (command deliveries) specified on a per-account basis. getmail also has excellent support for domain (multidrop) mailboxes, including delivering messages to different users or destinations based on the envelope recipient address.
GNU parallel is a shell tool for executing jobs in parallel locally or using remote computers. A job is typically a single command or a small script that has to be run for each of the lines in the input. The typical input is a list of files, a list of hosts, a list of users, a list of URLs, or a list of tables. If you use xargs today you will find GNU parallel very easy to use, as GNU parallel is written to have the same options as xargs. If you write loops in shell, you will find GNU parallel may be able to replace most of the loops and make them run faster by running several jobs in parallel. If you use ppss or pexec you will find GNU parallel will often make the command easier to read. GNU parallel makes sure output from the commands is the same output as you would get had you run the commands sequentially. This makes it possible to use output from GNU parallel as input for other programs.