Combating SPAM

The battle against SPAM is waged on two fronts: legal and technical. Legally, SPAM is not a violation in most governmental regions. In the United States, California leads the fight against SPAM, deeming SPAM a civil offense and fining spammers up to $50 per SPAM email.
Technically, you can configure Linux to block or otherwise filter SPAM. For example, many SPAM emails forge the delivery information, which MTAs and MDAs recognize and block. MTAs and MDAs can check information such as the sender's address, recipient's address, subject, or content for known spammers, known spammer keywords, or any other criteria.

A free framework called the Mail Abuse Prevention System (MAPS) Realtime Blackhole List (RBL) allows SPAM recipients to blacklist spammers. People who receive SPAM submit a copy of the email to administrators at MAPS RBL. The administrators decide if the mail is legitimate SPAM, and if so, put the spammer on the MAPS RBLblacklist^[1] .
SPAM recipients can also complain to their own system administrators. The administrators will analyze the email, and if legitimate SPAM, add the spammer to local blacklists.
These blacklists hold the IP addresses of known spammers. An MTA can check an incoming email's source IP address against either the local or the MAPS RBL blacklists and reject mail from a spammer who is on the list.

Email is one of the easiest techniques where we can transfer information and share data with others. However, it is also common to receive information or emails that contain malicious attachments or messages. Some email service providers filter and mark such spammy emails with the word SPAM in the subject of the email, indicating to the recipient that the email is either a junk email or unsolicited email with dubious content sent to numerous recipients by the sender. Clicking on links in such spam email may direct the recipient to a phishing web sites or download malware to the person's computer.
It is not surprising that most of us have encountered numerous spam emails in our inbox and believe it or not, your behavior online contributes to the spam messages that you receive.

Webcasting can be differentiated into three levels based on the degree of sophistication in the webcasting technologies used during the webcast.

1) An example of lowend webcasting is pushing information by e-mails. E-mail campaigns targeted at customers, suppliers, and business associates that have actually requested information are a proper use of the low-end webcasting to market products and build customer relations. The e-mails can include Web page links and audio and video files. Those unsolicited mass mailings via e-mail, usually called spams, do not discriminate the identity of the recipients and are sent from sources unknown to the audience. The spammers are under the scrutiny of state antispam laws and subject to prosecution.

The mid-range webcasting is the placing of video or audio content on a website and providing customers and associates with 24 hour access to current events and information about a company's products or services. The webcasting can be accompanied with features that enhance the video and audio experience. These features range from search engines or directories that help visitors to find specific information, to captioned and cued slides or diagrams that can be displayed along with the audio or video.

Applications may be either push or streaming, or a combination of the two. High-end webcasting is similar to traditional broadcasting because of its expected large audience. Nonetheless, it differs from traditional broadcasting by its video library accessible on demand, 24 hr a day. Businesses use high-end webcasting to disseminate information to remote office locations or to reach prospective customers or investors. The entertainment industry is also using high-end webcasting to enhance the viewing experience. Webcasters need to lease high-speed telephone lines, satellite delivery, and other ways of transmitting the live webcast signal to the Internet connection. They also need to purchase sufficient bandwidth that will meet the demand of the large number of people logging onto the server at the same time.

What's your experience with SPAM? Is it a major annoyance in your life, or a minor inconvenience that you tolerate in order to enjoy the greater advantages of email? Are you or anyone you know a spammer?
The next lesson concludes this module.

[1]Blacklist: A list of known email abusers, such as spammers.