There are a variety of antivirus software packages that operate in many different ways, depending on how the vendor chose to implement their software. What they have in common, though, is that they all look for patterns in the files or memory of your computer that indicate the possible presence of a known virus. Antivirus packages know what to look for through the use of virus profiles (sometimes called "signatures") provided by the vendor.
New viruses are discovered daily. The effectiveness of antivirus software is dependent on having the latest virus profiles installed on your computer so that it can look for recently discovered viruses. It is important to keep these profiles up to date.
More information about viruses and antivirus software can be found on the CERT Computer Virus Resource page
http://www.cert.org/other_sources/viruses.html
Wednesday, May 07, 2008
What is NAT?
Network Address Translation (NAT) provides a way to hide the IP addresses of a private network from the Internet while still allowing computers on that network to access the Internet. NAT can be used in many different ways, but one method frequently used by home users is called "masquerading".
Using NAT masquerading, one or more devices on a LAN can be made to appear as a single IP address to the outside Internet. This allows for multiple computers in a home network to use a single cable modem or DSL connection without requiring the ISP to provide more than one IP address to the user. Using this method, the ISP-assigned IP address can be either static or dynamic. Most network firewalls support NAT masquerading.
Using NAT masquerading, one or more devices on a LAN can be made to appear as a single IP address to the outside Internet. This allows for multiple computers in a home network to use a single cable modem or DSL connection without requiring the ISP to provide more than one IP address to the user. Using this method, the ISP-assigned IP address can be either static or dynamic. Most network firewalls support NAT masquerading.
Wednesday, February 27, 2008
CAPTCHA! Gmail bot detector system cracked
The Gmail CAPTCHA has been cracked—albeit not easily—raising new concerns about spammers' ability to abuse Google's e-mail services. Websense Security Labs pointed out the security breach late last week, noting that spammers have a lot to gain by being able to use bots to automatically sign up for new accounts.
Google's free e-mail services and a highly-desirable gmail.com domain—one that is unlikely to be blacklisted by anybody's spam filters—are just two of the features that induced spammers to crack the CAPTCHA and have bots do all the work. On the upside, it apparently wasn't easy—Websense says that it required two bot hosts to crack instead of just the one that recently cracked Windows Live Mail's CAPTCHA (Websense believes that the same group was involved with both). It also believes that the two hosts are required because the first host may fail at cracking the code the first time around (and possibly time out), but the second host may also be required to check the work of the first. Additionally, only one in every five CAPTCHA-breaking requests on Gmail succeeded. Still, a 20 percent success rate is relatively high when you consider that spambots are trying to register hundreds (or thousands) of e-mail addresses at a time.
The CAPTCHA test—Completely Automated Public Turing test to tell Computers and Humans Apart—is one we're all familiar with. When signing up for new services, we are often asked to decipher a series of letters and numbers embedded in an image that is supposed to be difficult for computers to read. But, while the CAPTCHA has worked well in the past, hackers are getting better at programming computers with the ability to read them.
Read More
Google's free e-mail services and a highly-desirable gmail.com domain—one that is unlikely to be blacklisted by anybody's spam filters—are just two of the features that induced spammers to crack the CAPTCHA and have bots do all the work. On the upside, it apparently wasn't easy—Websense says that it required two bot hosts to crack instead of just the one that recently cracked Windows Live Mail's CAPTCHA (Websense believes that the same group was involved with both). It also believes that the two hosts are required because the first host may fail at cracking the code the first time around (and possibly time out), but the second host may also be required to check the work of the first. Additionally, only one in every five CAPTCHA-breaking requests on Gmail succeeded. Still, a 20 percent success rate is relatively high when you consider that spambots are trying to register hundreds (or thousands) of e-mail addresses at a time.
The CAPTCHA test—Completely Automated Public Turing test to tell Computers and Humans Apart—is one we're all familiar with. When signing up for new services, we are often asked to decipher a series of letters and numbers embedded in an image that is supposed to be difficult for computers to read. But, while the CAPTCHA has worked well in the past, hackers are getting better at programming computers with the ability to read them.
Read More
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