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Detectionmediumtest

Office Application Initiated Network Connection To Non-Local IP

Detects an office application (Word, Excel, PowerPoint) that initiate a network connection to a non-private IP addresses. This rule aims to detect traffic similar to one seen exploited in CVE-2021-42292. This rule will require an initial baseline and tuning that is specific to your organization.

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Launch
Christopher Peacock, SCYTHE, Florian Roth (Nextron Systems), Tim Shelton, Nasreddine Bencherchali (Nextron Systems)Created Wed Nov 10Updated Fri Oct 1775e33ce3-ae32-4dcc-9aa8-a2a3029d6f84windows
Log Source
WindowsNetwork Connection
ProductWindows← raw: windows
CategoryNetwork Connection← raw: network_connection

Events for outbound and inbound network connections including DNS resolution.

Detection Logic
Detection Logic12 selectors
detection:
    selection:
        Image|endswith:
            - '\excel.exe'
            - '\outlook.exe'
            - '\powerpnt.exe'
            - '\winword.exe'
            - '\wordview.exe'
        Initiated: 'true'
    filter_main_local_ranges:
        DestinationIp|cidr:
            - '127.0.0.0/8'
            - '10.0.0.0/8'
            - '172.16.0.0/12'
            - '192.168.0.0/16'
            - '169.254.0.0/16'
            - '::1/128'  # IPv6 loopback
            - 'fe80::/10'  # IPv6 link-local addresses
            - 'fc00::/7'  # IPv6 private addresses
    filter_main_msrange_generic:
        DestinationIp|cidr:
            - '2.16.56.0/23' # Akamai International B.V.
            - '2.17.248.0/21' # Akamai International B.V.
            - '13.107.240.0/21' # Microsoft Corporation
            - '20.184.0.0/13' # Microsoft Corporation
            - '23.61.224.0/20' # Akamai-AS
            - '20.192.0.0/10' # Microsoft Corporation
            - '23.72.0.0/13' # Akamai International B.V.
            - '23.3.88.0/22' # Akamai-AS
            - '23.216.132.0/22' # Akamai-AS
            - '40.76.0.0/14' # Microsoft Corporation
            - '51.10.0.0/15' # Microsoft Corporation
            - '51.103.0.0/16' # Microsoft Corporation
            - '51.104.0.0/15' # Microsoft Corporation
            - '51.142.136.0/22' # Microsoft Corporation - https://ipinfo.io/AS8075/51.140.0.0/14-51.142.136.0/22
            - '52.160.0.0/11' # Microsoft Corporation - https://ipinfo.io/AS8075/52.160.0.0/11
            - '95.101.96.0/21' # Akamai-As
            - '204.79.197.0/24' # Microsoft Corporation
    filter_main_msrange_exchange_1:
        # Exchange Online
        # "urls": [
        #       "outlook.cloud.microsoft",
        #       "outlook.office.com",
        #       "outlook.office365.com"
        # ]
        DestinationIp|cidr:
            - '13.107.4.0/22'
            - '13.107.6.152/31'
            - '13.107.18.10/31'
            - '13.107.42.0/23'
            - '13.107.128.0/22'
            - '23.35.224.0/20'
            - '23.53.40.0/22'
            - '23.103.160.0/20'
            - '23.216.76.0/22'
            - '40.96.0.0/13'
            - '40.104.0.0/15'
            - '52.96.0.0/14'
            - '131.253.33.215/32'
            - '132.245.0.0/16'
            - '150.171.32.0/22'
            - '204.79.197.215/32'
            - '2603:1006::/40'
            - '2603:1016::/36'
            - '2603:1026::/36'
            - '2603:1036::/36'
            - '2603:1046::/36'
            - '2603:1056::/36'
            - '2620:1ec:4::152/128'
            - '2620:1ec:4::153/128'
            - '2620:1ec:c::10/128'
            - '2620:1ec:c::11/128'
            - '2620:1ec:d::10/128'
            - '2620:1ec:d::11/128'
            - '2620:1ec:8f0::/46'
            - '2620:1ec:900::/46'
            - '2620:1ec:a92::152/128'
            - '2620:1ec:a92::153/128'
        DestinationPort:
            - 80
            - 443
    filter_main_msrange_exchange_2:
        # Exchange Online
        # "urls": [
        #       "outlook.office365.com",
        #       "smtp.office365.com"
        # ]
        DestinationIp|cidr:
            - '13.107.6.152/31'
            - '13.107.18.10/31'
            - '13.107.128.0/22'
            - '23.103.160.0/20'
            - '40.96.0.0/13'
            - '40.104.0.0/15'
            - '52.96.0.0/14'
            - '131.253.33.215/32'
            - '132.245.0.0/16'
            - '150.171.32.0/22'
            - '204.79.197.215/32'
            - '2603:1006::/40'
            - '2603:1016::/36'
            - '2603:1026::/36'
            - '2603:1036::/36'
            - '2603:1046::/36'
            - '2603:1056::/36'
            - '2620:1ec:4::152/128'
            - '2620:1ec:4::153/128'
            - '2620:1ec:c::10/128'
            - '2620:1ec:c::11/128'
            - '2620:1ec:d::10/128'
            - '2620:1ec:d::11/128'
            - '2620:1ec:8f0::/46'
            - '2620:1ec:900::/46'
            - '2620:1ec:a92::152/128'
            - '2620:1ec:a92::153/128'
        DestinationPort:
            - 143
            - 587
            - 993
            - 995
        Protocol: 'tcp'
    filter_main_msrange_exchange_3:
        # Exchange Online
        # "urls": [
        #       "*.protection.outlook.com"
        #  ]
        DestinationIp|cidr:
            - '40.92.0.0/15'
            - '40.107.0.0/16'
            - '52.100.0.0/14'
            - '52.238.78.88/32'
            - '104.47.0.0/17'
            - '2a01:111:f400::/48'
            - '2a01:111:f403::/48'
        DestinationPort: 443
    filter_main_msrange_exchange_4:
        # Exchange Online
        # "urls": [
        #       "*.mail.protection.outlook.com",
        #       "*.mx.microsoft"
        #  ]
        DestinationIp|cidr:
            - '40.92.0.0/15'
            - '40.107.0.0/16'
            - '52.100.0.0/14'
            - '52.238.78.88/32'
            - '104.47.0.0/17'
            - '2a01:111:f400::/48'
            - '2a01:111:f403::/48'
        DestinationPort: 25
    filter_main_msrange_sharepoint_1:
        # SharePoint Online and OneDrive for Business",
        # "urls": [
        #       "*.sharepoint.com"
        # ]
        DestinationIp|cidr:
            - '13.107.136.0/22'
            - '40.108.128.0/17'
            - '52.104.0.0/14'
            - '104.146.128.0/17'
            - '150.171.40.0/22'
            - '2603:1061:1300::/40'
            - '2620:1ec:8f8::/46'
            - '2620:1ec:908::/46'
            - '2a01:111:f402::/48'
        DestinationPort:
            - 80
            - 443
        Protocol: 'tcp'
    filter_main_msrange_office_1:
        # Microsoft 365 Common and Office Online",
        # "urls": [
        #       "*.officeapps.live.com",
        #       "*.online.office.com",
        #       "office.live.com",
        #       "office.com.akadns.net"
        # ],
        DestinationIp|cidr:
            - '13.107.6.171/32'
            - '13.107.18.15/32'
            - '13.107.140.6/32'
            - '20.64.0.0/10'
            - '52.108.0.0/14'
            - '52.244.37.168/32'
            - '2603:1006:1400::/40'
            - '2603:1016:2400::/40'
            - '2603:1026:2400::/40'
            - '2603:1036:2400::/40'
            - '2603:1046:1400::/40'
            - '2603:1056:1400::/40'
            - '2603:1063:2000::/38'
            - '2620:1ec:c::15/128'
            - '2620:1ec:8fc::6/128'
            - '2620:1ec:a92::171/128'
            - '2a01:111:f100:2000::a83e:3019/128'
            - '2a01:111:f100:2002::8975:2d79/128'
            - '2a01:111:f100:2002::8975:2da8/128'
            - '2a01:111:f100:7000::6fdd:6cd5/128'
            - '2a01:111:f100:a004::bfeb:88cf/128'
        DestinationPort:
            - 80
            - 443
        Protocol: 'tcp'
    filter_main_msrange_office_2:
        # Microsoft 365 Common and Office Online
        # "urls": [
        #       "*.auth.microsoft.com",
        #       "*.msftidentity.com",
        #       "*.msidentity.com",
        #       "account.activedirectory.windowsazure.com",
        #       "accounts.accesscontrol.windows.net",
        #       "adminwebservice.microsoftonline.com",
        #       "api.passwordreset.microsoftonline.com",
        #       "autologon.microsoftazuread-sso.com",
        #       "becws.microsoftonline.com",
        #       "ccs.login.microsoftonline.com",
        #       "clientconfig.microsoftonline-p.net",
        #       "cloudapp.azure.com",
        #       "companymanager.microsoftonline.com",
        #       "device.login.microsoftonline.com",
        #       "graph.microsoft.com",
        #       "graph.windows.net",
        #       "login-us.microsoftonline.com",
        #       "login.microsoft.com",
        #       "login.microsoftonline-p.com",
        #       "login.microsoftonline.com",
        #       "login.windows.net",
        #       "logincert.microsoftonline.com",
        #       "loginex.microsoftonline.com",
        #       "nexus.microsoftonline-p.com",
        #       "passwordreset.microsoftonline.com",
        #       "provisioningapi.microsoftonline.com",
        #       "web.core.windows.net",
        # ]
        DestinationIp|cidr:
            - '172.128.0.0/10'
            - '20.20.32.0/19'
            - '20.103.156.88/32' # msn.com
            - '20.190.128.0/18'
            - '20.231.128.0/19'
            - '40.126.0.0/18'
            - '57.150.0.0/15'
            - '2603:1006:2000::/48'
            - '2603:1007:200::/48'
            - '2603:1016:1400::/48'
            - '2603:1017::/48'
            - '2603:1026:3000::/48'
            - '2603:1027:1::/48'
            - '2603:1036:3000::/48'
            - '2603:1037:1::/48'
            - '2603:1046:2000::/48'
            - '2603:1047:1::/48'
            - '2603:1056:2000::/48'
            - '2603:1057:2::/48'
        DestinationPort:
            - 80
            - 443
        Protocol: 'tcp'
    filter_main_msrange_office_3:
        # Microsoft 365 Common and Office Online
        #  "urls": [
        #       "*.compliance.microsoft.com",
        #       "*.data.microsoft.com",
        #       "*.protection.office.com",
        #       "*.security.microsoft.com",
        #       "compliance.microsoft.com",
        #       "defender.microsoft.com",
        #       "protection.office.com",
        #       "security.microsoft.com",
        #       "teams.microsoft.com",
        #  ]
        DestinationIp|cidr:
            - '13.64.0.0/11'
            - '13.107.6.192/32'
            - '13.107.9.192/32'
            - '13.89.179.14/32'
            - '20.40.0.0/14'
            - '20.48.0.0/12'
            - '20.64.0.0/12'
            - '52.123.0.0/16'
            - '52.108.0.0/14'
            - '52.136.0.0/13'
            - '57.150.0.0/15'
            - '80.239.150.67/32' # Arelion Sweden AB
            - '2620:1ec:4::192/128'
            - '2620:1ec:a92::192/128'
        DestinationPort: 443
        Protocol: 'tcp'
    filter_main_destination_host:
        DestinationHostname|endswith: '.deploy.static.akamaitechnologies.com'
        DestinationPort: 443
        Protocol: 'tcp'
    condition: selection and not 1 of filter_main_*
False Positives

You may have to tune certain domains out that Excel may call out to, such as microsoft or other business use case domains.

Office documents commonly have templates that refer to external addresses, like "sharepoint.ourcompany.com" may have to be tuned.

It is highly recommended to baseline your activity and tune out common business use cases.

References
1
Resolving title…
corelight.com
2
Resolving title…
learn.microsoft.com
MITRE ATT&CK
Rule Metadata
Rule ID
75e33ce3-ae32-4dcc-9aa8-a2a3029d6f84
Status
test
Level
medium
Type
Detection
Created
Wed Nov 10
Modified
Fri Oct 17
Author
Christopher Peacock, SCYTHE, Florian Roth (Nextron Systems), Tim Shelton, Nasreddine Bencherchali (Nextron Systems)
Path
rules/windows/network_connection/net_connection_win_office_outbound_non_local_ip.yml
Raw Tags
attack.executionattack.t1203
View on GitHub