There is malware exploiting a vulnerability in Microsoft
Word that is programmed to download additional malware onto Windows PCs,
according to a warning issued by Microsoft’s Malware Protection Center.
The bug was actually patched in November’s
Patch Tuesday, but the security team is reminding users about the update
to fix the RTF vulnerability after detecting the first pieces of malware in
the wild exploiting the flaw, the company said on Dec. 28. It had also updated
the bulletin several times since November to include updates for more
applications, according to the FAQ.
The patch exists for Microsoft Word 2002, 2003, 2007, and
2010 (both 32-big and 64-bit versions) for Windows. There is no fix as of yet
for Word 2004. Mac versions of Office have also been patched, according to the update,
named MS10-087.
The exploit involves using a malicious Rich Text Format file
to generate a stack overflow in Word, MMPC said. Once the user’s Word
installation has been compromised, the attack code downloads and executes
additional Trojans onto the computer, according to the security warning.
The exploit code is particularly efficient, as users don’t
need to manually open the malicious RTF file or the e-mail with the file
attached to be infected, Symantec said. The malware executes automatically if
users running Office 2007 or 2010 preview the e-mail in Outlook in its Reading
Pane, according to the security company. Alternatively, if the attacking e-mail
is the most recent message received, it opens automatically in the Reading Pane
when Outlook starts, said Symantec.
“In this scenario, this attack vector requires minimal user
action,” said Microsoft. Even if users are careful and not opening suspicious
messages, a majority of the users have Reading Pane enabled, the company said.
Microsoft also said that Outlook is not “directly” affected
because the malware executes only through Microsoft Word. However, because Word
is the default e-mail reader in Outlook 2007 and 2010, criminals using e-mail
to spread the malicious RTF files, present a particularly dangerous threat, the
company said.
The attacker gains the “same user rights as a local user,”
according to the alert, so the attack’s impact would vary by the way the user’s
account is configured on a given system. While all systems are vulnerable to
remote code execution, users with restricted rights would be affected less
severely than a user with administrative rights, according to the Microsoft.
The vulnerability was rated as “1” on Microsoft’s
exploitability index, meaning the team expected an exploit to appear within 30
days. The RTF bug is “critical” for Office 2007 and 2010 installations, but
“important” for Office XP and Office 2003, according to the Patch Tuesday
update. It is also “important” for the Open XML File format Converter for the
Mac as well as the Mac versions of Office – 2004, 2008, and 2011.
The patch fixes the bug by ensuring Office uses “a more
appropriate and secure search order” when loading libraries, according to the
warning.
The various viewer programs for Word, Excel, PowerPoint and
Visio are not vulnerable at this time, according to the MS10-087 page.
Article source: http://www.eweek.com/c/a/Security/Microsoft-Words-RTF-Bug-Targeted-by-Malware-160117/
Category: Virus/Malware