はじめに
このドキュメントでは、Cisco E メール セキュリティ アプライアンス(ESA)で受信する「Potential Directory Harvest Attack」エラー メッセージについて説明します。
警告メッセージ「Potential Directory Harvest Attack detected」は何を意味しますか。
ESAの管理者は、次のDirectory Harvest Attack Prevention(DHAP)警告メッセージを受信しました。
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
これらのアラートは情報アラートと見なされるため、アクションを実行する必要はありません。外部メールサーバが無効な受信者を大量に送信しようとしたため、DHAP(Directory Harvest Attack Prevention)アラートがトリガーされました。ESAは、メールポリシー設定に基づいて設定されたとおりに動作します。
リスナーがリモート・ホストから受信する1時間あたりの無効な受信者の最大数。このしきい値は、RAT拒否およびSMTPコールアヘッドサーバ拒否の合計数と、SMTPカンバセーションでドロップされた無効なLDAP受信者または作業キューでバウンスされた無効なLDAP受信者(関連するリスナーのLDAP受付設定で設定)へのメッセージの合計数を合わせた数を表します。LDAP受け入れクエリ用のDHAPの設定の詳細については、『Eメールセキュリティユーザガイド』の「LDAPクエリ」の章を参照してください。
アラートを受信しないようにするには、alertconfigでアラートプロファイルを調整して、これらのアラートをフィルタリングします。
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
または、GUIでSystem Administration > Alerts > Recipient Addressの順に選択し、受信した重大度を変更するか、アラート全体を変更します。
GUI
GUIからDHAPの設定パラメータを表示するには、Mail Policies > Mail Flow Policies > をクリックし、ポリシー名を編集するか、Default Policy Parameters >をクリックして、必要に応じてMail Flow Limits/Directory Harvest Attack Prevention (DHAP)セクションを変更します。
変更を送信し、GUIに確定します。
CLI を使う場合:
CLIからDHAPの設定パラメータを表示するには、listenerconfig > edit(編集するリスナーの番号を選択)> hostaccess > defaultを使用して、DHAP設定を編集します。
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]>
更新または変更を行った場合は、メインCLIプロンプトに戻り、すべての変更をコミットします。
関連情報