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files are specific to the sample we analyzed at HBGary, Inc.
The attackers must use a second stage download mechanism
to achieve full system access due to memory constraints. It
is unlikely that the final payload could be delivered through
the original exploit given these conditions. The dropper
is XOR encrypted with a 0x95 key. The shellcode copies
this encrypted binary to the user
s AppData directory as
a.exe
. The shellcode then decrypts
a.exe
and moves it
b.exe
in the same directory. Then
b.exe
is executed.
The following actionable intelligence can be used to identify
exploit remnants in the heap space of Internet Explorer post
exploitation attempt. These patterns can be searched for
when doing memory analysis
of a victim system.
SHELLCODE ARTIFACTS
PATTERN
Self-decrypting code using
a constant XOR value.
80 34 0B D8 80 34 0B D8
Kernel32.dll
searching code.
64 A1 30 00 00 00 8B 40 0C 8B 70 1C
Push Urlmon string to stack
using two push statements.
68 6F 6E 00 00 68 75 72 6C 6D
The following SNORT rules have been released by the Emerging
Threats project to detected the final payload command and
control communications.
Network Detection Signatures
alert tcp $HOME_NET any -> $EXTERNAL_NET 443 (msg:
ET TROJAN
Aurora Backdoor (C&C) client connection to CnC
; flow:established,to_
server; content:
|ff ff ff ff ff ff 00 00 fe ff ff ff ff ff ff ff ff ff 88 ff|
depth:20; flowbits:set,ET.aurora.init; classtype:trojan-activity;
reference:url,www.trustedsource.org/blog/373/An-Insight-into-theAurora-Communication-Protocol; reference:url,doc.emergingthreats.
net/2010695; reference:url,www.emergingthreats.net/cgi-bin/cvsweb.
cgi/sigs/VIRUS/TROJAN_Aurora; sid:2010695; rev:2;)
alert tcp $EXTERNAL_NET 443 -> $HOME_NET any (msg:
ET TROJAN
Aurora Backdoor (C&C) connection CnC response
; fl owbits:isset,ET.
aurora.init; flow:established,from_server; content:
|cc cc cc cc cd
cc cc cc cd cc cc cc cc cc cc cc|
; depth:16; classtype:trojan-activity;
reference:url,www.trustedsource.org/blog/373/An-Insight-into-theAurora-Communication-Protocol; reference:url,doc.emergingthreats.
net/2010696; reference:url,www.emergingthreats.net/cgi-bin/cvsweb.
cgi/sigs/VIRUS/TROJAN_Aurora; sid:2010696; rev:2;)
DROPPER
The initial dropper is merely a detonation package that
decompresses an embedded DLL into the Windows system32
directory and loads it as a service. The initial dropper is likely
to be packed (UPX, etc). The dropper has an embedded DLL
that is decompressed to the windows system32 directory. This
DLL will be named to resemble existing services (rasmon.
dll, etc). In order to evade forensics, the file-time of the
dropped DLL will be modified to match that of an existing
system DLL (user32.dll, etc). The dropped DLL is loaded into
its own svchost.exe process. Several registry keys are created
and then deleted as part of this process. Finally, the dropper
deletes itself from the system by using a dissolving batch file
(DFS.BAT, etc).
ACTIONABLE INTELLIGENCE
PATTERN
Service Key & Value
Note: deleted after drop
SOFTWARE\Microsoft\Windows NT\
CurrentVersion\SvcHost\
Value: SysIns
Data: Ups??? (??? are three random
chars)
Path to backdoor
Note: deleted after stage 1
SYSTEM\CurrentControlSet\Services\
Ups???\Parameters\
Value: ServiceDLL
Data: (full path to the backdoor)
Path to backdoor
Note: persistent
SYSTEM\CurrentControlSet\Services\
RaS???\Parameters\
Value: ServiceDLL
Data: (full path to the backdoor)
February 10, 2010 5
ACTIONABLE INTELLIGENCE
PATTERN
Potential variation
SYSTEM\CurrentControlSet\Services\
RaS???\Parameters\
Value: ServiceDLL
Data: %temp%\c_####.nls (where