Tutorial Blog – Online Free Tutorial Free online Tutorial blog

21Dec/090

GENERIC CIALIS on my website? I think my site has been hacked!

Has your site ever dropped suddenly from the index or disappeared mysteriously from search results? Have you ever received a notice that your site is using cloaking techniques? Unfortunately, sometimes a malicious party "hacks" a website: they penetrate the security of a site and insert undesirable content. Sophisticated attackers can camouflage this spammy or dangerous content so that it doesn't appear for normal users, and appears only to Googlebot, which could negatively impact your site in Google's results.

In such cases it used to be very difficult to detect the problem, because the site would appear normal in the eyes of the user. It may be possible that only requests with a User-agent: of Googlebot and coming from Googlebot's IP could see the hidden content. But that's over: with Fetch as Googlebot, the new Labs feature in Webmaster Tools, you can see exactly what Googlebot is seeing, and avoid any kind of cloaking problems. We'll show you how:

Let's imagine that Bob, the administrator of www.example.com, is searching for his site but he finds this instead:

That's strange, because when he looks at the source code of www.example.com, it looks fine:

With much surprise Bob may receive a notice from Google warning him that his site is not complying with Google's quality guidelines. Fortunately he has his site registered with Webmaster Tools, let's see how he can check what Googlebot sees:

First Bob logs into Webmaster Tools and selects www.example.com. The Fetch as Googlebot feature will be at the bottom of the navigation menu, in the Labs section:

The page will contain a field where you can insert the URL to fetch. It can also be left blank to fetch the homepage.

Bob can simply click Fetch and wait a few seconds. After refreshing the page, he can see the status of the fetch request. If it succeeds, he can click on the "Success" link...

...and that will show the details, with the content of the fetched page:

Aha! There's the spammy content! Now Bob can be certain that www.example.com has been hacked.

Confirming that the website has been hacked (and perhaps is still hacked) is an important step. It is, however, only the beginning. For more information, we strongly suggest getting help from your server administrator or hoster and reading our previous blog posts on the subject of hacked sites:

Source:  http://googlewebmastercentral.blogspot.com

  • Share/Bookmark
Filed under: Web Design No Comments
21Dec/091

Handling legitimate cross-domain content duplication

We've recently discussed several ways of handling duplicate content on a single website; today we'll look at ways of handling similar duplication across different websites, across different domains. For some sites, there are legitimate reasons to duplicate content across different websites — for instance, to migrate to a new domain name using a web server that cannot create server-side redirects. To help with issues that arise on such sites, we're announcing our support of the cross-domain rel="canonical" link element.

Ways of handling cross-domain content duplication:

  • Choose your preferred domain
    When confronted with duplicate content, search engines will generally take one version and filter the others out. This can also happen when multiple domain names are involved, so while search engines are generally pretty good at choosing something reasonable, many webmasters prefer to make that decision themselves.
  • Enable crawling and use 301 (permanent) redirects where possible
    Where possible, the most important step is often to use appropriate 301 redirects. These redirects send visitors and search engine crawlers to your preferred domain and make it very clear which URL should be indexed. This is generally the preferred method as it gives clear guidance to everyone who accesses the content. Keep in mind that in order for search engine crawlers to discover these redirects, none of the URLs in the redirect chain can be disallowed via a robots.txt file. Don't forget to handle your www / non-www preference with appropriate redirects and in Webmaster Tools.
  • Use the cross-domain rel="canonical" link element
    There are situations where it's not easily possible to set up redirects. This could be the case when you need to move your website from a server that does not feature server-side redirects. In a situation like this, you can use the rel="canonical" link element across domains to specify the exact URL of whichever domain is preferred for indexing. While the rel="canonical" link element is seen as a hint and not an absolute directive, we do try to follow it where possible.

Still have questions?

Q: Do the pages have to be identical?
A: No, but they should be similar. Slight differences are fine.

Q: For technical reasons I can't include a 1:1 mapping for the URLs on my sites. Can I just point the rel="canonical" at the homepage of my preferred site?
A: No; this could result in problems. A mapping from old URL to new URL for each URL on the old site is the best way to use rel="canonical".

Q: I'm offering my content / product descriptions for syndication. Do my publishers need to use rel="canonical"?
A: We leave this up to you and your publishers. If the content is similar enough, it might make sense to use rel="canonical", if both parties agree.

Q: My server can't do a 301 (permanent) redirect. Can I use rel="canonical" to move my site?
A: If it's at all possible, you should work with your webhost or web server to do a 301 redirect. Keep in mind that we treat rel="canonical" as a hint, and other search engines may handle it differently. But if a 301 redirect is impossible for some reason, then a rel="canonical" may work for you. For more information, see our guidelines on moving your site.

Q: Should I use a noindex robots meta tag on pages with a rel="canonical" link element?
A: No, since those pages would not be equivalent with regards to indexing - one would be allowed while the other would be blocked. Additionally, it's important that these pages are not disallowed from crawling through a robots.txt file, otherwise search engine crawlers will not be able to discover the rel="canonical" link element.

Source:  http://googlewebmastercentral.blogspot.com

  • Share/Bookmark
Filed under: Web Design 1 Comment
8Dec/090

How E-mail Works

Every day, the citizens of the Internet send each other billions of e-mail messages. If you're online a lot, you yourself may send a dozen or more e-mails each day without even thinking about it. Obviously, e-mail has become an extremely popular communication tool.

Have you ever wondered how e-mail gets from your computer to a friend halfway around the world? What is a POP3 server, and how does it hold your mail? The answers may surprise you, because it turns out that e-mail is an incredibly simple system at its core. In this article, we'll take an in-depth look at e-mail and how it works.

An E-mail Message
According to Darwin Magazine: Prime Movers, the first e-mail message was sent in 1971 by an engineer named Ray Tomlinson. Prior to this, you could only send messages to users on a single machine. Tomlinson's breakthrough was the ability to send messages to other machines on the Internet, using the @ sign to designate the receiving machine.

An e-mail message has always been nothing more than a simple text message -- a piece of text sent to a recipient. In the beginning and even today, e-mail messages tend to be short pieces of text, although the ability to add attachments now makes many messages quite long. Even with attachments, however, e-mail messages continue to be text messages -- we'll see why when we get to the section on attachments.

E-mail Clients
You've probably already received several e-mail messages today. To look at them, you use some sort of e-mail client. Many people use well-known, stand-alone clients like Microsoft Outlook, Outlook Express, Eudora or Pegasus. People who subscribe to free e-mail services like Hotmail or Yahoo use an e-mail client that appears in a Web page. If you're an AOL customer, you use AOL's e-mail reader. No matter which type of client you're using, it generally does four things:

  • Shows you a list of all of the messages in your mailbox by displaying the message headers. The header shows you who sent the mail, the subject of the mail and may also show the time and date of the message and the message size.
  • Lets you select a message header and read the body of the e-mail message.
  • Let's you create new messages and send them. You type in the e-mail address of the recipient and the subject for the message, and then type the body of the message.
  • Lets you add attachments to messages you send and save the attachments from messages you receive.

Source:  http://communication.howstuffworks.com/email.htm

  • Share/Bookmark
Filed under: Uncategorized No Comments
8Dec/090

Melissa Macro Virus

A complete revision history is at the end of this file.

Systems Affected

  • Machines with Microsoft Word 97 or Word 2000
  • Any mail handling system could experience performance problems or a denial of service as a result of the propagation of this macro virus.

    • Overview

    At approximately 2:00 PM GMT-5 on Friday March 26 1999 we began receiving reports of a Microsoft Word 97 and Word 2000 macro virus which is propagating via email attachments. The number and variety of reports we have received indicate that this is a widespread attack affecting a variety of sites.

    Our analysis of this macro virus indicates that human action (in the form of a user opening an infected Word document) is required for this virus to propagate. It is possible that under some mailer configurations, a user might automatically open an infected document received in the form of an email attachment. This macro virus is not known to exploit any new vulnerabilities. While the primary transport mechanism of this virus is via email, any way of transferring files can also propagate the virus.

    Anti-virus software vendors have called this macro virus the Melissa macro or W97M_Melissa virus.

    I. Description

    The Melissa macro virus propagates in the form of an email message containing an infected Word document as an attachment. The transport message has most frequently been reported to contain the following Subject header 

    Subject: Important Message From <name>

    Where <name> is the full name of the user sending the message.

    The body of the message is a multipart MIME message containing two sections. The first section of the message (Content-Type: text/plain) contains the following text. 

    Here is that document you asked for ... don't show anyone else ;-)

    The next section (Content-Type: application/msword) was initially reported to be a document called "list.doc". This document contains references to pornographic web sites. As this macro virus spreads we are likely to see documents with other names. In fact, under certain conditions the virus may generate attachments with documents created by the victim.

    When a user opens an infected .doc file with Microsoft Word97 or Word2000, the macro virus is immediately executed if macros are enabled.

    Upon execution, the virus first lowers the macro security settings to permit all macros to run when documents are opened in the future. Therefore, the user will not be notified when the virus is executed in the future.

    The macro then checks to see if the registry key

    "HKEY_Current_User\Software\Microsoft\Office\Melissa?" has a value of "... by Kwyjibo". If that registry key does not exist or does not have a value of "... by Kwyjibo", the virus proceeds to propagate itself by sending an email message in the format described above to the first 50 entries in every Microsoft Outlook MAPI address book readable by the user executing the macro. Keep in mind that if any of these email addresses are mailing lists, the message will be delivered to everyone on the mailing lists. In order to successfully propagate, the affected machine must have Microsoft Outlook installed; however, Outlook does not need to be the mailer used to read the message.

    This virus can not send mail on systems running MacOS; however, the virus can be stored on MacOS.

    Next, the macro virus sets the value of the registry key to "... by Kwyjibo". Setting this registry key causes the virus to only propagate once per session. If the registry key does not persist through sessions, the virus will propagate as described above once per every session when a user opens an infected document. If the registry key persists through sessions, the virus will no longer attempt to propagate even if the affected user opens an infected document.

    The macro then infects the Normal.dot template file. By default, all Word documents utilize the Normal.dot template; thus, any newly created Word document will be infected. Because unpatched versions of Word97 may trust macros in templates the virus may execute without warning. For more information please see:

    http://www.microsoft.com/security/bulletins/ms99-002.asp Finally, if the minute of the hour matches the day of the month at this point, the macro inserts into the current document the message "Twenty-two points, plus triple-word-score, plus fifty points for using all my letters. Game's over. I'm outta here."

    Note that if you open an infected document with macros disabled and look at the list of macros in this document, neither Word97 nor Word2000 list the macro. The code is actually VBA (Visual Basic for Applications) code associated with the "document.open" method. You can see the code by going into the Visual Basic editor.

    If you receive one of these messages, keep in mind that the message came from someone who is affected by this virus and they are not necessarily targeting you. We encourage you to contact any users from which you have received such a message. Also, we are interested in understanding the scope of this activity; therefore, we would appreciate if you would report any instance of this activity to us according to our Incident Reporting Guidelines document available at:

    http://www.cert.org/tech_tips/incident_reporting.html

    II. Impact

    • Users who open an infected document in Word97 or Word2000 with macros enabled will infect the Normal.dot template causing any documents referencing this template to be infected with this macro virus. If the infected document is opened by another user, the document, including the macro virus, will propagate. Note that this could cause the user's document to be propagated instead of the original document, and thereby leak sensitive information.
    • Indirectly, this virus could cause a denial of service on mail servers. Many large sites have reported performance problems with their mail servers as a result of the propagation of this virus.

    III. Solutions

    • Block messages with the signature of this virus at your mail transfer agents or other central point of control.

    • Utilize virus scanners

      Most virus scanning tools will detect and clean macro viruses. In order to detect and clean current viruses you must keep your scanning tools up to date with the latest definition files.

    • Encourage users at your site to disable macros in Microsoft Word

      Notify all of your users of the problem and encourage them to disable macros in Word. You may also wish to encourage users to disable macros in any product that contains a macro language as this sort of problem is not limited to Microsoft Word. In Word97 you can disable automatic macro execution (click Tools/Options/General then turn on the 'Macro virus protection' checkbox). In Word2000 macro execution is controlled by a security level variable similar to Internet Explorer (click on Tools/Macro/Security and choose High, Medium, or Low). In that case, 'High' silently ignores the VBA code, Medium prompts in the way Word97 does to let you enable or disable the VBA code, and 'Low' just runs it.

      Word2000 supports Authenticode on the VB code. In the 'High' setting you can specify sites that you trust and code from those sites will run.

    • General protection from Word Macro Viruses

      For information about macro viruses in general, we encourage you to review the document "Free Macro AntiVirus Techniques" by Chengi Jimmy Kuo which is available at.

      http://www.nai.com/services/support/vr/free.asp

    Additional Information
    • Share/Bookmark
    Filed under: Anti Virus, Spam & Spyware No Comments
    8Dec/090

    How Computer Viruses Work

    Strange as it may sound, the computer virus is something of an Information Age marvel. On one hand, viruses show us how vulnerable we are -- a properly engineered virus can have a devastating effect, disrupting productivity and doing billions of dollars in damages. On the other hand, they show us how sophisticated and interconnected human beings have become.

    For example, experts estimate that the Mydoom worm infected approximately a quarter-million computers in a single day in January 2004. Back in March 1999, the Melissa virus was so powerful that it forced Microsoft and a number of other very large companies to completely turn off their e-mail systems until the virus could be contained. The ILOVEYOU virus in 2000 had a similarly devastating effect. In January 2007, a worm called Storm appeared -- by October, experts believed up to 50 million computers were infected. That's pretty impressive when you consider that many viruses are incredibly simple.

    When you listen to the news, you hear about many different forms of electronic infection. The most common are:

    • Viruses - A virus is a small piece of software that piggybacks on real programs. For example, a virus might attach itself to a program such as a spreadsheet program. Each time the spreadsheet program runs, the virus runs, too, and it has the chance to reproduce (by attaching to other programs) or wreak havoc.
    • E-mail viruses - An e-mail virus travels as an attachment to e-mail messages, and usually replicates itself by automatically mailing itself to dozens of people in the victim's e-mail address book. Some e-mail viruses don't even require a double-click -- they launch when you view the infected message in the preview pane of your e-mail software [source: Johnson].
    • Trojan horses - A Trojan horse is simply a computer program. The program claims to do one thing (it may claim to be a game) but instead does damage when you run it (it may erase your hard disk). Trojan horses have no way to replicate automatically.
    • Worms - A worm is a small piece of software that uses computer networks and security holes to replicate itself. A copy of the worm scans the network for another machine that has a specific security hole. It copies itself to the new machine using the security hole, and then starts replicating from there, as well.

    ­Source:  http://www.howstuffworks.com/virus.htm

    • Share/Bookmark
    Filed under: Anti Virus, Spam & Spyware No Comments
       Older Entries »

    Categories

    Archives

    Meta

    Recent Posts

    RSS Technology news and tips

    RSSTwitter: itcrate