Post on 23-Feb-2016
description
Solutions to Spam
----Presented by Di Xu17.12.2010
Introduction
Overview of Spam
Solutions to Spam
Conclusion
Agenda
Advertising material sent by email to people who have not asked for it.(Oxford dictionary)
An electronic message is "spam" if (A) the recipient's personal identity and context are irrelevant because the message is equally applicable to many other potential recipients; AND (B) the recipient has not verifiably granted deliberate, explicit, and still-revocable permission for it to be sent(C) the transmission and reception of the message appears to the recipient to give a disproportionate benefit to the sender.
Introduction -Definition
Too many recipients
No header or use forged header
Forged sender’s address
The content of email with specific HTML tag
The body of email consists of small font size
Email subject consists of email address or recipient name
Introduction -Characteristics
From web pages
By guessing & cleaning
From white and yellow pages
From a previous owner of the email address
Buying lists from others
Overview of Spam -How to harvest email addresses
webmail
Third-party computers
Open relays
Open proxies
Spammer viruses
Overview of Spam -How to send Spam
IP Blocking◦ Blacklist◦ Whitelist◦ Greylist
Spam Filtering◦ Rule-based filter◦ Checksum-based filter◦ Content-based filter
Honeypot email address
Payment-based approach
Solutions of Spam -For administrator of email system
Blacklist: A blacklist is a list of known IP addresses that are used to send spam
and the earliest anti-spam technology.
Disadvantage: cannot control emails from unlisted email addresses
Solutions to Spam -IP Blocking
Whitelist: The method makes users may get email from trusted contacts or
domain, but reject emails from not already known domain and contacts, which restricts communication
Disadvantage:◦ It is not a good solution to a big enterprise
◦ It is not difficult for spammers to guess domain which is whitelisted
Solutions to Spam - IP Blocking
Greylist: It is decided by not only IP address, but also some more information
of e-mail like envelope data. If the e-mail is the first time sent to the e-mail account, it will be rejected. But the information of e-mail will be stored
Disadvantage:◦ greylist leads to deliver email in delay before resent email will be
confirmed to send
◦ some normal emails cannot be delivered
Solutions to Spam -IP Blocking
Rule-based Filtering: Users can design the rules to filter e-mail
Disadvantage:◦ It is not flexible
Solutions to Spam -Spam Filter
Checksum-based Filtering: sometimes referred to collaborative filtering.
distributed checksum clearinghouse(DCC) Vipul’s Razor
Disadvantage:◦ It costs a comparative high license fee
◦ if spammers insert something unique invisible to the body of email, it will lead to different checksum
Solutions to Spam -Spam Filter
Content filtering: the solution is content-based filters which scan the nature content of
spam to measure whether it is spam or not
Disadvantage:◦ For some rare spam words, Bayesian could decrease the
probability of the email is spam
◦ It cannot filter email which consist of no words only image
Solutions to Spam -Spam Filter
Honeypot Email address: It is forged email addresses which pollute spammers’
address database
Disadvantage:◦ It is difficult to ◦ keep ideal situation
Solution to Spam - Honeypot Email Address
Payment-based approach: the e-mail servers require payment to delivery e-mail to the
recipients for the senders. But the payment can be the real currency or something else somehow like cost of senders’computing
Disadvantage:◦ The difficulty of the calculations required must be increased over time
Solution to Spam - Payment-based approach
SpamAssassin is one of the hybrid filtering methods. It uses content-based filter and real-time blacklists.
A system which uses whitelist, blacklist and content filter.
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Solution to Spam - Other Anti-spam approach
United States CAN-SPAM Act of 2003
Canada Electronic Commerce Protection Act
Australia Spam Act 2003
Solutions to Spam -Legislation Enforcement
Select an Unusual E-mail Address
Disposable Addresses
Use Provided Filtering Systems
Never reply to Spam and never use the Unsubscribe Link
Solutions to Spam -Anti-spam behaviors for users
Combination of different solutions could be the most effective solution
Anti-spam solutions do not only rely on anti-spam technology, but also users’ good behavior to protect their own email addresses
Conclusion