Editing Email attachment (section)

==Malware==
{{See also|Spamming}}
A lot of [[malware]] is distributed via email attachments with some even considering such to be the main [[Vector (malware)|vector]] for cyberattacks on businesses.<ref name=techa>{{cite web|last1=Martin|first1=Jim|title=Here's what you need to do to protect your PC from ransomware and NotPetya|url=http://www.techadvisor.co.uk/feature/security/what-is-ransomware-how-do-i-protect-my-pc-from-petya-3659036/|publisher=Tech Advisor|access-date=29 June 2017}}</ref><ref>{{cite web|title=Truth on zero-day attacks|url=https://www.pcr-online.biz/news/read/truth-on-zero-day-attacks/039452|publisher=PCR|access-date=29 June 2017}}</ref><ref>{{cite book|last1=Aycock|first1=John|title=Computer Viruses and Malware|date=2006|publisher=Springer|isbn=9780387341880|url=https://books.google.com/books?id=xnW-qvk1gzkC&pg=PA142|access-date=29 June 2017|language=en}}</ref> Users are advised to be extremely cautious with attachments and to not open any attachments that are not from a trusted source and expected<!--by the recipient--> − even if the sender is in their address book as their account might have been taken over or misused.<ref name=techa/><ref>{{cite book|last1=Miller|first1=Michael R.|title=Microsoft Security Essentials User Manual (Digital Short Cut)|date=2009|publisher=Pearson Education|isbn=9780768695298|url=https://books.google.com/books?id=wVAfzSIMD-4C&pg=PT95|access-date=29 June 2017|language=en}}</ref><ref>{{cite book|last1=Vermaat|first1=Misty E.|title=Enhanced Discovering Computers, Essentials|date=2014|publisher=Cengage Learning|isbn=9781285845531|url=https://books.google.com/books?id=XBIeCgAAQBAJ&pg=PA23|access-date=29 June 2017|language=en}}</ref> While many email servers scan attachments for malware and block dangerous filetypes, this should not be relied upon − especially as such cannot detect [[Zero-day (computing)|zero-day exploits]].<ref>{{cite web|title=How To Spot A Dangerous Email Attachment|url=http://www.makeuseof.com/tag/spot-dangerous-email-attachment/|publisher=MakeUseOf|access-date=29 June 2017}}</ref> 

===Dangerous file types===
Email users are typically warned that unexpected email with attachments should always be considered suspicious and dangerous, particularly if not known to be sent by a trusted source. However, in practice this advice is not enough – "known trusted sources" were the senders of [[Computer program|executable programs]] creating mischief and mayhem as early as 1987 with the mainframe-based [[Christmas Tree EXEC]].

Since the [[ILOVEYOU]] and [[Anna Kournikova (computer virus)|Anna Kournikova]] [[Computer worm|worms]] of 2000 and 2001, email systems have increasingly added layers of protection to prevent potential [[malware]]. Now, many block certain types of attachments.<ref>[http://mail.google.com/support/bin/answer.py?hl=en&answer=6590 ''"Some file types are blocked"'', mail.google.com].</ref><ref>[http://support.microsoft.com/kb/829982 ''"You may receive an "Outlook blocked access to the following potentially unsafe attachments" message in Outlook"'', microsoft.com].</ref>