Wat betekent de waarschuwing "Potential Directory Harvest Attack Detected"?

Inleiding

Dit document beschrijft de foutmelding "Potential Directory Harvest Attack" zoals deze is ontvangen op de Cisco Email Security Applicatie (ESA).

Wat betekent de waarschuwing "Potential Directory Harvest Attack Detected"?

Beheerders van de ESA hebben het volgende DHAP-waarschuwingsbericht (Directory Harvest Attack Prevention) ontvangen:

The Warning message is:

Potential Directory Harvest Attack detected. See the system mail logs for more
information about this attack.

Version: 8.0.1-023
Serial Number: XXBAD1112DYY-008X011
Timestamp: 22 Sep 2014 21:21:32 -0600

Deze waarschuwingen worden beschouwd als informatie en u hoeft geen actie te ondernemen. Een externe mailserver heeft te veel ongeldige ontvangers geprobeerd en heeft de DHAP-waarschuwing (Directory Harvest Attack Prevention) geactiveerd. De ESA handelt zoals geconfigureerd op basis van de posterijen.  

Dit is het maximale aantal ongeldige ontvangers per uur dat de luisteraar ontvangt van een externe host. Deze drempel vertegenwoordigt het totale aantal RAT-afwijzingen en SMTP-call-ahead-serverafwijzingen in combinatie met het totale aantal berichten aan ongeldige LDAP-ontvangers dat in het SMTP-gesprek is gevallen of in de werkrij is opgeslagen (zoals geconfigureerd in de LDAP accepteer instellingen op de bijbehorende luisteraar). Voor meer informatie over het configureren van DHAP voor LDAP accepteert queries, zie het hoofdstuk "LDAP Queries" van de e-mail security gebruikershandleiding. 

U kunt uw waarschuwingsprofiel aanpassen met alertconfig om deze te filteren als u deze waarschuwingen niet wilt ontvangen:

myesa.local> alertconfig

Sending alerts to:
 robert@domain.com
 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. robert@domain.com (all)
[]> 1

Choose the Alert Class to modify for "robert@domain.com".
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

Of van de GUI System Administration > Waarschuwingen > Ontvangeradres en wijzig de ontvangen ernst, of waarschuwing in zijn geheel.  

GUI

Om uw DHAP configuratieparameters van de GUI te bekijken, klik via Mail Policies > Mail Flow Policies > Klik op de Policy Name om te bewerken, of standaard Policy Parameters > en breng wijzigingen aan in de Mail Flow Limits/Directory Harvest Attack Prevention (DHAP) sectie zoals nodig:

Verzend en voer uw wijzigingen in de GUI in.

CLI

Om uw DHAP-configuratieparameters van de CLI te bekijken, gebruikt u listenerconfig > edit (het nummer van de te bewerken luisteraar kiezen) > hostaccess > default om de DHAP-instellingen te bewerken:

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. 
[10]> 

Enter the maximum number of messages per connection. 
[10]> 

Enter the maximum number of recipients per message. 
[50]> 

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.
[25]> 

Select an action to apply when a recipient is rejected due to DHAP:
1. Drop
2. Code
[1]> 

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.
[550]> 

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
[1]> 

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]> 

Als u updates of wijzigingen aanbrengt, gaat u terug naar de belangrijkste CLI-prompt en legt u alle wijzigingen vast.

Gerelateerde informatie

• Cisco e-mail security applicatie – eindgebruikershandleiding
• Technische ondersteuning en documentatie – Cisco Systems