Why are some attachments blocked or renamed? |
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Attachment filtering is increasingly important in today's environment, where many attachments contain harmful viruses or malicious material that may cause significant damage to the user's computer or to the organization as a whole by damaging important documentation or releasing sensitive information to the public. These attachments are stripped out by our Exchange mail system. A message is sent to internal users when an attachment is blocked (whether they are the sender or receiver).
If you do need to send these files (which you consider safe and legitimate), you have two options:
- Compress your file and attach it as a compressed archive (zip, rar, gz, 7z, etc). We recommend using compressed archives which support encrypted file names. This will increase the chances of the email and attachment reaching the recipient.
- Post the file on your website and send the link to the recipient (password protect the file using password protected compressed archives if it contains sensitive information).
- Users can also collaborate and share files using file hosting services such as Dropbox, Windows Live Mesh, Google Docs, etc. To see a comparison of these and other alternatives, please refer to Wikipedia’s comparison of file hosting services
- The Campus also hosts a SharePoint server to collaborate and share files securely, discussion boards, project wiki’s, blogs, shared calendars, etc. with other colleagues on campus.
This filtering is only applicable to external users; that is, attachment filtering is not performed when users internal to the department send email to other internal users but only when email goes to outside users, or received from outside users. Please note that this does not guarantee that your email or attachment will reach the recipient. Each organization has their own policies regarding email and attachment filtering.
Following industry best practices, the following files are blocked:
| Extension | Type of file |
| *.ace* | Archive file |
| *.ade* | Microsoft Access project extension |
| *.adp* | Microsoft Access project |
| *.adt* | ACT! document template |
| *.app* | Executable application |
| *.asp* | Active Server Page files |
| *.arj* | Archive file |
| *.asd* | Word files that always have macros |
| *.bas* | Microsoft Visual Basic class module |
| *.bat* | Batch file |
| *.bin* | Binary file |
| *.btm* | Batch to memory batch file |
| *.cbt* | Computer based training |
| *.ceo* | Virus |
| *.chm* | Compiled HTML help file |
| *.cmd* | Microsoft Windows command script |
| *.cla* | Java class file |
| *.com* | Microsoft MS-DOS program |
| *.cpl* | Control Panel extension |
| *.crt* | Security certificate |
| *.csc* | Corel script file |
| *.css* | Cascading Style Sheet file |
| *.dll* | DLL files |
| *.drv* | Driver files |
| *.exe* | Program executable |
| *.email* | Outlook Express e-mail message |
| *.fon* | Font file |
| *.hlp* | Help file |
| *.hta* | HTML program |
| *.inf* | Setup information |
| *.ins* | Internet naming service |
| *.isp* | Internet communication settings |
| *.je* | JScript file |
| *.js* | JScript file |
| *.jse* | JScript encoded script file |
| *.lib* | Program library common object file format |
| *.lnk* | Shortcut |
| *.mdb* | Access database file |
| *.mde* | MDE database file |
| *.mht* | Archived Web page |
| *.msc* | Microsoft common console document |
| *.msi* | Microsoft Windows installer package |
| *.mso* | Math script object file |
| *.msp* | Microsoft Windows installer patch |
| *.mst* | Microsoft Visual test source files |
| *.obj* | Relocatable object code |
| *.ocx* | Object Linking and Embedding control executable |
| *.ov* | OrgViewer file |
| *.pcd* | Photo CD image, Microsoft Visual compiled script |
| *.pgm* | CGI program |
| *.pif* | Shortcut to MS-DOS program |
| *.prc* | Palm Pilot resource file |
| *.reg* | Registration entries |
| *.scr* | Screen saver |
| *.sct* | Windows script component |
| *.shb* | Shortcut into a document |
| *.shs* | Shell scrap object |
| *.smm* | AMI Pro macro |
| *.swf* | Macromedia files |
| *.sys* | System device driver |
| *.url* | Internet shortcut |
| *.vb* | VBScript file |
| *.vxd* | Virtual device driver |
| *.wsc* | Windows script component |
| *.wsf* | Windows script file |
| *.wsh* | Windows script host settings file |
| *}* | CLSID filter |
In the case of a virus outbreak or security issue, we may be forced to block additional files to protect our students, faculty and staff. We will keep the users notified regarding any such event.
Other organizations are also filtering attachments:
Google GmailUniversity of Washington
Seattle Pacific University
University of Denver
Indiana University
Rutgers University