F-Secure Virus Descriptions : NetSky.N
[Summary] | [Disinfection] | [Detailed Description] | [Detection]
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The Netsky.N variant was discovered on March 16th 2004. The worm is
similar to its predecessors in the family. The only major difference
is that a fake note claiming the message to be virus free is added to
the infected messages.
F-Secure provides the special disinfection utility to eliminate
Netsky.N worm infection. You can download this utility from our
ftp site:
ftp://ftp.f-secure.com/anti-virus/tools/f-netsky.exe
ftp://ftp.f-secure.com/anti-virus/tools/f-netsky.zip
Disinfection instructions can be found here:
ftp://ftp.f-secure.com/anti-virus/tools/f-netsky.txt
System administrators who are using F-Secure Policy Manager,
can distribute the tool as a JAR package automatically to all
workstations.
System administrators can download the JAR version from:
http://www.europe.f-secure.com/tools/f-netsky.jar
ftp://ftp.europe.f-secure.com/anti-virus/tools/f-netsky.jar
System Infection
Upon execution the worm copies itself to the Windows System Directory
with the filename 'VisualGuard.exe' which is added to the registry as
[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run] =
"NetDy" = "%SysDir%\VisualGuard.exe"
The worm removes several registry values that belong to other worms.
Email Propagation
When collecting addresses NetSky.N recursively walks through all hard
drives and checks the content of files with the following extensions:
.pl
.htm
.html
.eml
.txt
.php
.asp
.wab
.doc
.vbs
.rtf
.uin
.shtm
.cgi
.dhtm
.adb
.tbb
.dbx
.sht
.oft
.msg
.jsp
.wsh
.xml
The email messages are randomly composed from different components. For
example the subjects are made of the following texts:
"Re:"
"Re: Re:"
"your "
"my "
"approved "
"important "
"document"
"file"
"details"
"information"
"letter"
"product"
"website"
"application"
"screensaver"
"bill"
"word document"
"excel document"
"data"
"message"
"text"
"document_all"
"here"
"hi"
"hello"
"thanks!"
"approved"
"corrected"
"patched"
"improved"
"important"
"read it immediately"
Email bodies are chosen from many different predefined texts:
"Please see the attached file for details."
"Please read the attached file."
"Your document is attached."
"Please read the document."
"Your file is attached."
"Your document is attached."
"Please confirm the document."
"Please read the important document."
"See the file."
"Requested file."
"Authentication required."
"Your document is attached to this mail."
"I have attached your document."
"I have received your document. The corrected document is attached."
"Your document."
"Your details."
The attachment names are hardcoded and can be one of
"document.exe"
"your_details.scr"
"doc.pif"
"doc.txt<lots of spaces>.exe"
"document.htm<lots of spaces>.scr"
"your_details.doc<lots of spaces>.exe"
Detection for this malware was published on March 16th, 2004
in the following F-Secure Anti-Virus updates:
[FSAV_Database_Version]
Version=2004-03-16_01
Technical Details:
Gergely Erdelyi, March 16th, 2004;
Description Updated:
Alexey Podrezov, March 18th, 2004;
F-Secure Corporation
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