Outlook and Attachment Security

Outlook and Attachment Security Some of most common attachments you receive, such as JPG and GIF images, are entirely safe. Others, such as Word or Excel documents, are usually safe but could carry macro viruses
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Outlook and Attachment Security[ Team LiB ]Outlook and Attachment SecuritySome of most common attachments you receive, such as JPG and GIF images, areentirely safe. Others, such as Word or Excel documents, are usually safe but could carrymacro viruses. Other attachments, including those with .exe, .js, and .pif extensions,might be safe, but theyre just as often viruses. Because its impossible to know for sure,its important that you not only install a virus scanner, but also use its autoprotect featureand keep the virus signatures current. You should never open files you arent expecting,even if your antivirus scanner gives them a clean bill of health—the virus might be toonew to be in your virus definitions.Just in case youre lax when it comes to keeping your antivirus scanner up-to-date,Outlook offers some built-in protection against email viruses, including blocking all filetypes that have the potential to carry viruses and are executable. Although you canunblock any or all the file types, you should unblock only the file types that you really doneed or use other methods to retrieve the attachments. Many corporate firewalls block the same extensions that Outlook blocks, and you might have to change the extension or zip the file before sending attachments to some contacts. If youd like all of your attachments zipped before sending, look for ZipOut, the WinZip Outlook add-in or other utilities at http://www.slipstick.com.When you send blocked file types as attachments, you should get in the habit of changingfile extensions to a safe, nonexecutable type or zipping the file. Outlook 2003 wont warnyou when you attach a blocked file type, but it will warn you before you send it, as shownin Figure 6.5. Choose No, zip or add an underscore to the filename, and then reattach.This ensures that the person you send it to can access it also.Figure 6.5. When you send attachments that could carry viruses, Outlook alerts you before sending. If you edited your Registry to allow some file types, you wont see the warning when you send these file types.Blocked Attachment File TypesWhen you receive a file with any of the extensions listed in Table 6.1, Outlook hides theattachment from you to prevent you from opening it and infecting your computer system.In reality, you can still retrieve the attachment in several ways, including editing theRegistry to allow access to a specific file type, accessing your mailbox using a differentmail program, or asking the person to zip the file and resend it. Table 6.1. File Attachment Types Blocked by Outlook 2003 Attachment Extension Program Associated with the Extension.app Visual FoxPro Application.ade Microsoft Access project.adp Microsoft Access project.bas Microsoft VB/VBA code module.bat Batch file.chm Compiled HTML help file.cmd Microsoft Windows NT command script.com Microsoft MS-DOS program.cpl Control Panel extension.crt Security certificate.csh C Shell program.exe Executable program.fxp Visual FoxPro compiled program.hlp Help file.hta HTML program.inf Setup information.ins Internet naming service.isp Internet communication settings.js JScript file.jse JScript-encoded script file.ksh Korn Shell program.lnk Shortcut.mda Microsoft Access add-in program.mdb Microsoft Access program.mde Microsoft Access MDE database.mdz Microsoft Access wizard program.msc Microsoft Common Console document.msi Windows Installer package.msp Windows Installer patch.mst Visual Test source files.pcd Photo CD image or Visual Test compiled script.pif Program information file.prf Microsoft Outlook Profile Settings.prg Visual FoxPro Program.pst Outlook Personal Folders file.reg Windows Registry entries.scf Windows Explorer command.scr Screen saver.sct Windows script component.shb Shortcut into a document.shs Shell scrap object.url Internet shortcut.vb VBScript file.vbe VBScript-encoded script file.vbs VBScript file.wsc Windows script component.wsf Windows script file.wsh Windows script host settings file.xsl XML file that can contain scriptWhen you receive a message that contains a blocked attachment, Outlook places the textshown in Figure 6.6 in the message header. The attachment icon is visible and allmessages with blocked attachments are included in the Large Messages Search Folder. Figure 6.6. Outlooks InfoBar alerts you to the fact that a blocked attachment is in the message and includes the filename.Accessing Blocked AttachmentsMany people find it easiest to edit the Registry and always allow some file types,especially when they use the Attachment Options add-in fromhttp://www.slovaktech.com. Editing the Registry to allow all files isnt the brightest idea in the world and could result in a virus infection. For this reason, unblock only the extensions for the attachment types you need to access regularly, not all the file types. If you dont normally get any blocked attachment types, remove or rename the level1remove key when you save the attachment you need.Outlook is programmed to block certain file types that Microsoft calls Level1attachments. Thes ...