These alerts are considered informational and you should not need to take any action. An outside mail server attempted too many invalid recipients and triggered the DHAP (Directory Harvest Attack Prevention) alert. The ESA is acting as configured based on the mail policy configuration.
This is the maximum number of invalid recipients per hour the listener will receive from a remote host. This threshold represents the total number of RAT rejections and SMTP call-ahead server rejections combined with the total number of messages to invalid LDAP recipients dropped in the SMTP conversation or bounced in the work queue (as configured in the LDAP accept settings on the associated listener). For more information on configuring DHAP for LDAP accept queries, see the "LDAP Queries" chapter of the Email Security User Guide.
You can adjust your alert profile with alertconfig to filter these out if you do not wish to receive these alerts:
Sending alerts to: firstname.lastname@example.org Class: All - Severities: All
Initial number of seconds to wait before sending a duplicate alert: 300 Maximum number of seconds to wait before sending a duplicate alert: 3600 Maximum number of alerts stored in the system are: 50
Alerts will be sent using the system-default From Address.
Cisco IronPort AutoSupport: Enabled You will receive a copy of the weekly AutoSupport reports.
Choose the operation you want to perform: - NEW - Add a new email address to send alerts. - EDIT - Modify alert subscription for an email address. - DELETE - Remove an email address. - CLEAR - Remove all email addresses (disable alerts). - SETUP - Configure alert settings. - FROM - Configure the From Address of alert emails. > edit
Please select the email address to edit. 1. email@example.com (all) > 1
Choose the Alert Class to modify for "firstname.lastname@example.org". Press Enter to return to alertconfig. 1. All - Severities: All 2. System - Severities: All 3. Hardware - Severities: All 4. Updater - Severities: All 5. Outbreak Filters - Severities: All 6. Anti-Virus - Severities: All 7. Anti-Spam - Severities: All 8. Directory Harvest Attack Prevention - Severities: All
Or from the GUI System Administration > Alerts > Recipient Address and modify the severity's received, or alert in its entirety.
To view your DHAP configuration parameters from the GUI, click through Mail Policies > Mail Flow Policies > Click the Policy Name to edit, or Default Policy Parameters > and make changes to the Mail Flow Limits/Directory Harvest Attack Prevention (DHAP) section as needed:
Submit and Commit your changes to the GUI.
To view your DHAP configuration parameters from the CLI, use listenerconfig > edit (choosing the number of the listener to edit) > hostaccess > default to edit the DHAP settings:
Default Policy Parameters ========================== Maximum Message Size: 10M Maximum Number Of Concurrent Connections From A Single IP: 10 Maximum Number Of Messages Per Connection: 10 Maximum Number Of Recipients Per Message: 50 Directory Harvest Attack Prevention: Enabled Maximum Number Of Invalid Recipients Per Hour: 25 Maximum Number Of Recipients Per Hour: Disabled Maximum Number of Recipients per Envelope Sender: Disabled Use SenderBase for Flow Control: Yes Spam Detection Enabled: Yes Virus Detection Enabled: Yes Allow TLS Connections: No Allow SMTP Authentication: No Require TLS To Offer SMTP authentication: No DKIM/DomainKeys Signing Enabled: No DKIM Verification Enabled: No SPF/SIDF Verification Enabled: No DMARC Verification Enabled: No Envelope Sender DNS Verification Enabled: No Domain Exception Table Enabled: No Accept untagged bounces: No
There are currently 5 policies defined. There are currently 8 sender groups.
Choose the operation you want to perform: - NEW - Create a new entry. - EDIT - Modify an entry. - DELETE - Remove an entry. - MOVE - Move an entry. - DEFAULT - Set the defaults. - PRINT - Display the table. - IMPORT - Import a table from a file. - EXPORT - Export the table to a file. - RESET - Remove senders and set policies to system default. > default
Enter the default maximum message size. Add a trailing k for kilobytes, M for megabytes, or no letter for bytes. [10M]>
Enter the maximum number of concurrent connections allowed from a single IP address. >
Enter the maximum number of messages per connection. >
Enter the maximum number of recipients per message. >
Do you want to override the hostname in the SMTP banner? [N]>
Would you like to specify a custom SMTP acceptance response? [N]>
Would you like to specify a custom SMTP rejection response? [N]>
Do you want to enable rate limiting per host? [N]>
Do you want to enable rate limiting per envelope sender? [N]>
Do you want to enable Directory Harvest Attack Prevention per host? [Y]>
Enter the maximum number of invalid recipients per hour from a remote host. >
Select an action to apply when a recipient is rejected due to DHAP: 1. Drop 2. Code >
Would you like to specify a custom SMTP DHAP response? [Y]>
Enter the SMTP code to use in the response. 550 is the standard code. >
Enter your custom SMTP response. Press Enter on a blank line to finish.
Would you like to use SenderBase for flow control by default? [Y]>
Would you like to enable anti-spam scanning? [Y]>
Would you like to enable anti-virus scanning? [Y]>
Do you want to allow encrypted TLS connections? 1. No 2. Preferred 3. Required 4. Preferred - Verify 5. Required - Verify >
Would you like to enable DKIM/DomainKeys signing? [N]>
Would you like to enable DKIM verification? [N]>
Would you like to change SPF/SIDF settings? [N]>
Would you like to enable DMARC verification? [N]>
Would you like to enable envelope sender verification? [N]>
Would you like to enable use of the domain exception table? [N]>
Do you wish to accept untagged bounces? [N]>
If you make any updates or changes, return to the main CLI prompt and commit all changes.