Email Collection
Sub-techniques (3)
Adversaries may target user email to collect sensitive information. Emails may contain sensitive data, including trade secrets or personal information, that can prove valuable to adversaries. Adversaries can collect or forward email from mail servers or clients.
Procedure Examples |
|
| Name | Description |
|---|---|
| Silent Librarian |
Silent Librarian has exfiltrated entire mailboxes from compromised accounts.(Citation: DOJ Iran Indictments March 2018) |
| Magic Hound |
Magic Hound has compromised email credentials in order to steal sensitive data.(Citation: Certfa Charming Kitten January 2021) |
Mitigations |
|
| Mitigation | Description |
|---|---|
| Multi-factor Authentication |
Use two or more pieces of evidence to authenticate to a system; such as username and password in addition to a token from a physical smart card or token generator. |
| Email Collection Mitigation |
Use of encryption provides an added layer of security to sensitive information sent over email. Encryption using public key cryptography requires the adversary to obtain the private certificate along with an encryption key to decrypt messages. Use of two-factor authentication for public-facing webmail servers is also a recommended best practice to minimize the usefulness of user names and passwords to adversaries. Identify unnecessary system utilities or potentially malicious software that may be used to collect email data files or access the corporate email server, and audit and/or block them by using whitelisting (Citation: Beechey 2010) tools, like AppLocker, (Citation: Windows Commands JPCERT) (Citation: NSA MS AppLocker) or Software Restriction Policies (Citation: Corio 2008) where appropriate. (Citation: TechNet Applocker vs SRP) |
| Encrypt Sensitive Information |
Protect sensitive information with strong encryption. |
| Audit |
Perform audits or scans of systems, permissions, insecure software, insecure configurations, etc. to identify potential weaknesses. |
Detection
There are likely a variety of ways an adversary could collect email from a target, each with a different mechanism for detection.
File access of local system email files for Exfiltration, unusual processes connecting to an email server within a network, or unusual access patterns or authentication attempts on a public-facing webmail server may all be indicators of malicious activity.
Monitor processes and command-line arguments for actions that could be taken to gather local email files. Remote access tools with built-in features may interact directly with the Windows API to gather information. Information may also be acquired through Windows system management tools such as Windows Management Instrumentation and PowerShell.
Detection is challenging because all messages forwarded because of an auto-forwarding rule have the same presentation as a manually forwarded message. It is also possible for the user to not be aware of the addition of such an auto-forwarding rule and not suspect that their account has been compromised; email-forwarding rules alone will not affect the normal usage patterns or operations of the email account.
Auto-forwarded messages generally contain specific detectable artifacts that may be present in the header; such artifacts would be platform-specific. Examples include X-MS-Exchange-Organization-AutoForwarded set to true, X-MailFwdBy and X-Forwarded-To. The forwardingSMTPAddress parameter used in a forwarding process that is managed by administrators and not by user actions. All messages for the mailbox are forwarded to the specified SMTP address. However, unlike typical client-side rules, the message does not appear as forwarded in the mailbox; it appears as if it were sent directly to the specified destination mailbox.(Citation: Microsoft Tim McMichael Exchange Mail Forwarding 2) High volumes of emails that bear the X-MS-Exchange-Organization-AutoForwarded header (indicating auto-forwarding) without a corresponding number of emails that match the appearance of a forwarded message may indicate that further investigation is needed at the administrator level rather than user-level.
Связанные риски
Каталоги
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