Sourcefire Vulnerability Research Team Labs

What would you do with a pointer and a size?

Why do we need a new detection framework?

 Attacks have switched from server attacks to
client attacks
 Common attack vectors are easily obfuscated
 JavaScript
 Compression
 File formats are made by insane people
 Looking at you Flash and OLE guy…
 Back-channel systems are increasingly
difficult to detect

 Inline systems must emulate the processing
of 1000s of desktops
 Detection of many backchannels is most
successful with statistical evaluation of
network traffic

 Broadly speaking, IDS systems deal with
packet-by-packet inspection with some level
of reassembly
 Broadly speaking, AV systems typically target
indicators of known bad files or system states
“…the argument put forward that there's something wrong with anti-virus
products that don't detect metasploit output is fallacious on 2 counts: 1) the
output isn't necessarily malware (usually only greyware), and 2) anti-virus
products are not the proper defense against known exploits (patching is).”
-- Kurt Wismer

 A system is needed that can handle varied
detection needs
 A system is needed that extensible, open and
scalable
 A system is needed that facilitates incident
response, not just triggers it

 So……

Near-Realtime Detection Framework or:
“Anything is Possible”

 The heart of the NRT system
 APIs to handle:
 Deep Inspection Nugget registration
 Data Handler registration
 Detection requests
 Alerting
 Full analysis logging
 Output to API compliant systems
 Database driven

• Implements a database to provide a
centralized set of file information and
• Handles incoming queries for Data
Handlers that have failed local cache
hits
• Handles detection requests from
both Data Handlers and DINs
• Handles incoming results from Deep
Inspection Nuggets
• Handles database updates based on
DIN data
• Writes out verbose logging based on
DIN data
• Provides alerting to Data Handlers

 Capture data and metadata
 Contact dispatcher for handling
 Has this file been evaluated before?
 Where should I send it?
 Pass that data set to a Deep Inspection Nugget
 Accept feedback from the Dispatcher for
detection request
 Asynchronous alerting
 Local cache of detection outcome

• Data (in this case a file) is captured
• Metadata is captured (in this case
URL and filename)
• A local cache of MD5 sums and URLs
of files previously collected
• A library to handle managing the
initial file evaluation, cache checks and
communication with the Dispatcher

 Must handle data transfer from Data
Handlers
 Must communicate with Dispatcher
 Register detection capability
 Request for additional processing of
subcomponents
 Provide alerting feedback to Dispatcher

• Registers with the Dispatcher
• Processes data provided by the Data
Handlers, as instructed by the
Dispatcher
• Handles incoming queries for Data
Handlers that have failed local cache
hits
• Handles detection requests from
both Data Handlers and DINs
• Handles incoming results from Deep
Inspection Nuggets
• Handles database updates based on
DIN data
• Writes out verbose logging based on
DIN data
• Provides alerting to Data Handlers

 Provide entry to the system for any arbitrary
data type
 Determine and manage detection based on a
registered DIN
 Provide alerting to any framework capable
system
 Provide verbose, detailed logging on the
findings of the Nugget Farm
 Make intelligent use of all data discovered
during the evaluation process

An implementation of the NRT goals on a Snort platform
Target: Malicious pdf files

Sourcefire Vulnerability Research Team Labs

Let’s pretend that the PDF nugget already has the data…

Why are we passing back files?

 MD5 is stored for files and subcomponents
both bad and good
 Primarily this is used to avoid reprocessing
files we’ve already looked at
 But after a update to any DIN, all known-
good entries are “tainted”

 After an update to
detection, previously
analyzed files may be
found to be bad
 We don’t rescan all
files
 But if we see a match
for md5 to a previous
file, we will alert
retroactively

 When a subcomponent alerts, it is stored for
logging in its fully normalized state.
 If a file is bad, when the DIN completes
detection it passes the file to the Dispatcher
 Response teams have the entire file as well as
each portion that alerted in an easily
analyzed format

 Verbose data back to Data Handler should also be as verbose
as possible
 In this case we place data into the payload and provide a
custom message to Snort so we can use established
methods of handling Snort alerts
 04/16-16:38:48.1271450328 [**] [300:3221225473:1]
URL:/users/pusscat/jbig2.pdf Hostname:metasploit.com Alert
Info:Probable exploit of CVE-2009-0658 (JBIG2) detected in object 8,
declared as /Length 33/Filter [/FlateDecode/ASCIIHexDecode/JBIG2Decode
] [**] {TCP} 64.214.53.2:0 -> 216.75.1.230:0
04/16-16:38:48.12714503280:0:0:0:0:0 -> 0:0:0:0:0:0 type:0x800 len:0x0
64.214.53.2:0 -> 216.75.1.230:0 TCP TTL:240 TOS:0x10 ID:0 IpLen:20 DgmLen:1280
***AP*** Seq: 0x0 Ack: 0x0 Win: 0x0 TcpLen: 20
55 52 4C 3A 2F 75 73 65 72 73 2F 70 75 73 73 63 URL:/users/pussc
61 74 2F 6A 62 69 67 32 2E 70 64 66 20 48 6F 73 at/jbig2.pdf Hos
74 6E 61 6D 65 3A 6D 65 74 61 73 70 6C 6F 69 74 tname:metasploit
2E 63 6F 6D 20 41 6C 65 72 74 20 49 6E 66 6F 3A .com Alert Info:
50 72 6F 62 61 62 6C 65 20 65 78 70 6C 6F 69 74 Probable exploit
20 6F 66 20 43 56 45 2D 32 30 30 39 2D 30 36 35 of CVE-2009-065
38 20 28 4A 42 49 47 32 29 20 64 65 74 65 63 74 8 (JBIG2) detect
65 64 20 69 6E 20 6F 62 6A 65 63 74 20 38 2C 20 ed in object 8,
64 65 63 6C 61 72 65 64 20 61 73 20 2F 4C 65 6E declared as /Len
67 74 68 20 33 33 2F 46 69 6C 74 65 72 20 5B 2F gth 33/Filter [/
46 6C 61 74 65 44 65 63 6F 64 65 2F 41 53 43 49 FlateDecode/ASCI
49 48 65 78 44 65 63 6F 64 65 2F 4A 42 49 47 32 IHexDecode/JBIG2
44 65 63 6F 64 65 20 5D 20 Decode ]

Seriously, what would you do with a pointer and a size?

 Create file format templates which parse our
elements and provide you a datastructure

 Provide a full, common, scripting language
interface to create rules (Ruby? Python? Both?)

 Only do the heavy work (templating) once per
file format.

JBIG, ASCII Hex Decoding & Inflation

04/21-11:17:58.1271873878 [**] [300:3221225473:1] URL:/wrl/first.pdf
Hostname:wrl Alert Info:Probable exploit of CVE-2009-0658 (JBIG2)
detected in object 8, declared as /Length 29/Filter
[/FlateDecode/ASCIIHexDecode/JBIG2Decode ] [**] {TCP} 192.168.0.1:0
-> 204.15.227.178:0
04/21-11:17:58.12718738780:0:0:0:0:0 -> 0:0:0:0:0:0 type:0x800 len:0x0
192.168.0.1:0 -> 204.15.227.178:0 TCP TTL:240 TOS:0x10 ID:0 IpLen:20
DgmLen:1280
***AP*** Seq: 0x0 Ack: 0x0 Win: 0x0 TcpLen: 20
55 52 4C 3A 2F 77 72 6C 2F 66 69 72 73 74 2E 70 URL:/wrl/first.p
64 66 20 48 6F 73 74 6E 61 6D 65 3A 77 72 6C 20 df Hostname:wrl
41 6C 65 72 74 20 49 6E 66 6F 3A 50 72 6F 62 61 Alert Info:Proba
62 6C 65 20 65 78 70 6C 6F 69 74 20 6F 66 20 43 ble exploit of C
56 45 2D 32 30 30 39 2D 30 36 35 38 20 28 4A 42 VE-2009-0658 (JB
49 47 32 29 20 64 65 74 65 63 74 65 64 20 69 6E IG2) detected in
20 6F 62 6A 65 63 74 20 38 2C 20 64 65 63 6C 61 object 8, decla
72 65 64 20 61 73 20 2F 4C 65 6E 67 74 68 20 32 red as /Length 2
39 2F 46 69 6C 74 65 72 20 5B 2F 46 6C 61 74 65 9/Filter [/Flate
44 65 63 6F 64 65 2F 41 53 43 49 49 48 65 78 44 Decode/ASCIIHexD
65 63 6F 64 65 2F 4A 42 49 47 32 44 65 63 6F 64 ecode/JBIG2Decod
65 20 5D 20 e ]
=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
=+

What is that JavaScript up to?

[**] [300:2147483653:1] URL:/wrl/first.pdf Hostname:wrl
Alert Info:The JavaScript variables in object 6,
declared as /Length 5994/Filter
[/FlateDecode/ASCIIHexDecode ] , show a high degree of
entropy [**]

You tell me, does this string of variable names look weird to you?

EvctenMNtrWDQVBKGrwGxrxKfMiZoYziRxAFEfjMdXRzjGNqVZYEAqogviSvzHp
GpCkihcVtXRWcHphvhAnPOXnrxmTXJEUIkcYzelWZUCuIyKArtJvcEQXzUjHEzu
SjGEJugOyFQnaSplNWwQsqOoV

[**] [300:2147483649:1] URL:/wrl/first.pdf Hostname:wrl
Alert Info:Found in the Javascript block, while
searching object 6: unescape [**]

Wait, did someone say unescape…

 Sig up some common GetEIP techiniques…

 Heuristically hunt down shellcode decoder stubs

 Decode and parse shellcode

 Give back some REAL data.

What is that unescape up to….

[**] [300:3221225482:1] URL:/wrl/first.pdf
Hostname:wrl Alert Info:Reverse TCP
connectback shellcode detected. Connecting
to 10.4.4.10 on port 4444 [**]

Looking at the following:
Gave us the shellcode type as well
10 d4 77 74 71 20 f6 d3 e0 70 66 0c 7a 40 73 72 as the IP and port combination the
78 2f be 37 04 91 a8 46 93 41 1c 24 b0 b4 b1 3d
43 b5 96 15 7d 4e 9b 7e 48 42 8d 12 f7 eb 4f 0d connect back goes to.
7b 4a 25 08 d5 1d 0b ff c6 c0 e3 03 f5 b3 b2 34
71 18 fd ba 75 77 25 3c b8 7b 30 d4 43 78 1c 2a
.
. Wouldn’t it be great if something
.
bf 98 35 a5 af 98 1d 1f e0 17 95 0a 3a 5f 1f f0 knew to start listening?
87 c2 71 f1 e5 a0 77 f5 fe 94 fc 13 85 d8 23 a2
87 51 d0 81 8e 37 a0 70 2f bc 79 0a a1 c0 00 19
87 38 c0 57 b9 37 a0 9f ef a2 71 a3 b8 a0 77 2c
27 97 8a 20 64 fe 1f b5 87 c8 65 f5 ef 9e 1f f5
87 90 d1 a6 0a 37 a0 66 bc a2 75 a3 bc 9f 1d f7
36 00 2a 0a 3a c9 b6 dc 29 4d 83 80 03 0b 75 f5

 Take that IP address and Port, and auto-tcpdump
when you get an alert

 Watch everything the attacker does over that back
channel on the fly

 Poor-man’s netwitness. (Can I say that?)

 How about a custom post-mortem debugger on
every enterprise desktop?

 Have it alert to your central dispatcher and dump
whatever loaded file is the crash culprit.

 Get both failed exploit attempts and possibly a few
free 0-day to sell on the side!

 Make use of BinCrowd!
 Yank down the a whole community’s set of symbols for
that questionable sample you just got a hold of – malware
reuses code too!
 Not all of your machines have hardware DEP?
 Run one machine with DEP, use that custom post mortem,
still get near real time knowledge of attacks
 DLP is serious business
 Store more than one checksum type for sensitive data.
Custom nuggets can make it easy.

 We have hosted on http://labs.snort.org a package that contains:
 Snort Preprocessor for snagging .exe, .dll and .pdf files from live traffic
 A commented library that will allow you to thread calls to a detection
function
 A “Dumb Nugget” to simply write these files to disk
 A “Clam Nugget” to pass these files to ClamAV
 Local cache system to reduce detection overhead
 Alerting system that fires Snort alerts with arbitrary data
 Disclaimer
 For serious, this code was put together to pitch the idea to
management it is…well it is what it is
 This project is a research project in the VRT no timeline for release
either as open source or a Sourcefire product has been determined
 We’ll update it as we integrate the full dispatcher->data handler-
>deep inspection nugget code

 System Architects:
 Matthew Olney
 Lurene Grenier
 Patrick Mullen
 Nigel Houghton
 Programmers:
 Ryan Pentney (OMG CODE OUTPUT)
 Alain Zidouemba (ClamAV integration)
 Database:
 Alex Kambis
 File Format Research
 Monica Sojeong Hong
 Alex Kirk
 Infrastructure Support
 Kevin “McLovin” Miklavcic
 Christopher McBee
 Head Didn’t Fire Us During POC phase
 Matthew Watchinski, Sr. Director, Vulnerability Research

Blog:
http://vrt-sourcefire.blogspot.com/
Place we store bad ideas:
http://labs.snort.org/
Twitter:
@vrt_sourcefire (VRT Twitter Account)
@kpyke (Matthew Olney)
@pusscat (Lurene Grenier)
@xram_lrak (Matthew Watchinski)

Sourcefire Vulnerability Research Team Labs

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