E-mail is an essential communication tool that has been greatly abused by spam sender to disseminate unwanted information (messages) and spread malicious contents to Internet users. Current Internet technologies accelerated the distribution of spam. Effective controls need to be deployed to countermeasure the ever growing spam problem. Spam filters provide better protective mechanisms that are able to control spam. This paper summarizes most common techniques used for anti-spam filtering by analyzing the e-mail content and also looks into IP`s adopted to detect and control spam. Each filter has its own strengths and limitations. Depending upon the scenarios different kind of filters is effective on their suitable scenarios.
Spam is anonymous, unsolicited bulk email from the recipients point of view, it is unwanted detritus that chokes up their inboxes. Spam has become a part of our everyday lives. It is indicative of what is happening to the global economy. When looked at as a whole it is clear that the themes and development trends of spam closely correlate to the global financial situation. More than 70% of global email traffic consists of spam. Dealing with spam incurs high costs for organizations, prompting efforts to try to reduce spam-related costs by installing spam filters. This is called as spam filter mechanism. The individual efficiency of a spam filter installation depends on the amount of spam that is received and on the level of knowledge about spam.
Spam filters are mainly categorized as list based and content based spam filters. List-based filters attempt to stop spam by categorizing senders as spammers or trusted users, and blocking or allowing their messages accordingly. The various types of filters in this category are Blacklist filters, Real time Blackhole list and Whitelist filters. Content Based Filters rather than enforcing across-the-board policies for all messages from a particular email or IP address, content-based filters evaluate words or phrases found in each individual message to determine whether an email is spam or legitimate.
Spyware refers to programs that steal the user information stored in the user`s computer and transmit this information via the Internet to a designated home server without the user being aware of this transmission. These malware compromise every Internet user`s privacy by collecting detailed user profiles that can be used for commercial the user`s e-mail address, geographic location, web-surfing habits etc.
Users may not be aware that there is a lot of private information stored in their computers, or they cannot see the value of information from the point of view of marketing companies.
The working mechanism of common spyware is rather simple. They try to find out their interested information from your files in the hard disk and system`s settings (e.g. Microsoft Window`s Registry), according to the predefined list of locations. More " intelligent" spyware can do so by getting instructions from a central server depending on the system information collected enough information, they will transfer the stolen data back to the home server.
There are many anti-spyware products in the market. The mechanism of these anti-spyware products can mainly be classified into two categories: Signature Scanning and Network Filtering.
The technique of signature scanning is similar to the same technique applied in the anti-virus software. Basically, for each known spyware, a sequence of bytes, called the spyware signature, is identified. These signatures are stored in a database. The anti-spyware program checks the suspected software against this database. If the software matches any signature, it is considered to be a spyware. Signature scanning can only identify known spyware and users have to update the database frequently.
Firewall is for protecting and controlling the interface between a private network and an insecure, public network. Packet sniffer enables users to view the packet being transported out of the computer.In these years, network filtering technologies such as personal firewall and packet sniffer are also used as an anti-spyware solution.