Detecting Email Server Forgery

Most of the spam I see has been sent by servers forging or otherwise obscuring their server identity.  RFC2505 states that the server identity and sender address are easily forged.  Of these, it is easiest to identify server forgery.  Very little, if any, of the personal email has a forged server identity.  Unfortunately, legitimate bulk and automated email often shows signs of server identity.   If you deliver either of these types of email this article will provide information of fixing the situation.

The rules here apply email originating from the Internet only.    Mail User Agents submitting email are expected to violate these rules.  MUAs should use an authenticated encrypted connection to the Submission port (576).  Relay servers should not apply these rules to connections originating form the local network. Continue reading “Detecting Email Server Forgery”

Securing your Email Reputation with SPF

SPF (Server Policy Framework) is a simple means to limit the ability of  others to forge your identity in email.  I first implemented it after a forged identity under my domain was used to send Spam.  Once SPF was configured,  the bounce messages quickly dropped off.

Although not as frequently implemented as sender address checks, SPF can  be used to prevent forgery of the HELO identity.  My mail server uses SPF to check the Identity of the server.  This is easier to configure and more reliable than checking the domain in the Mail from address.  Even though I treat Neutral and Softfail policies as a Fail policy, I have not detected any false negatives.   I verify both the address returned by the PTR record for the host and the address in the HELO command.  This is primarily because the PTR record is more likely to have a valid domain. Continue reading “Securing your Email Reputation with SPF”

Setting Up BackupPC on Windows

My original intent in setting up BackupPC was to be able to backup my laptops. The mainly run Windows, and have a lot of shared files. Therefore I wanted a backup solution which handled de-duplication. BackupPC was just what I needed. I have already posted an article about Setting Up BackupPC on Ubuntu that includes setting up a server.

This article covers setting up BackupPC on Windows using rsyncd as the protocol.   (I tried using Samba, but didn’t like the results with Windows Home editions.) This is done with an extremely minimal cygwin install available from the BackupPC site on SourceForge.  The backups described here are not designed for bare metal recovery.   They should include all the user’s files, and some of the configuration data for installed applications. Continue reading “Setting Up BackupPC on Windows”

Setting Up BackupPC on Ubuntu

I recently started to do regular backups of all my systems using BackupPC. It uses the rsync protocol to limit the amount of data transferred during backups. Once the initial backup is done, future backups only need to copy incremental changes. This requires far less resources than other software I have used

This article covers setting up the server on Ubuntu and configuring backups for Ubuntu and OpenWRT. A future article will cover backing up Windows systems using an rsyncd daemon process. Continue reading “Setting Up BackupPC on Ubuntu”

Email Logins for Dovecot and Exim

While I was cleaning up my Ubuntu Email server configuration, I consolidated my login security.  My SMTP server is Exim and my IMAP server is Dovecot.  Mail User Agents (MUAs) use authentication over TLS encrypted connections to access IMAP and SMTP.   Both programs had their own password configuration.

Exim includes Dovecot in its supported authentication mechanisms.  This enables one authentication mechanism to be used for both SMTP and IMAP (or POP3).   This post also includes configuration details for forced authentication over the Submission port. Continue reading “Email Logins for Dovecot and Exim”

Implementing IPv6 Part 2

We are quickly running out of IPv4 addresses. Are you ready for World IPv6 Day on June 8th, 2011? I have prepared my configuration on OpenWRT and Ubuntu. This includes configuring DNS using bind, email using Exim, and a Squid web proxy.

Having verified that I could establish IPv6 connectivity, I chose to improve my connectivity. This started with getting a tunnel from Hurricane Electric and updating my configuration. I then updated my bind server and Exim mail server support IPv6 addresses. This posting updates and continues from my post on Implementing IPv6 6to4 on OpenWRT.   Review it for information on creating a tunnel and running radvd on OpenWRT. Continue reading “Implementing IPv6 Part 2”

Blocking Spam with Exim

Recent reports indicate that spam is increasing again.  I have been using Exim to filter spam for several years.  Some recent tuning I have done have decreased the percent of spam which reaches my spam filters.   This article provides a discussion of the techniques used, and provides implementation examples.   Spambots tend to be simple programs which don’t handle slow servers very well.   Using a greylist is effective method of blocking them as they usually don’t retry.   My latest changes use delays to cause many spambots to abandon their attempt.  Greylisting is used only for poorly configured servers that make it to the Recipient command.

Continue reading “Blocking Spam with Exim”

Email Policy

SysteMajik.com actively discourages Spam and email sent from incorrectly configured servers. Legitimate email from correctly configured servers should have little problem being delivered. We believe we are relatively complaint with  RFC 2505 – Anti-Spam Recommendations for SMTP MTAs and other RFCs mentioned at the end of this document.

This article covers our  policy implementation for incoming and outgoing email.  These policies apply to all email destined to or originating from systemajik.com,  toucantango.com, and other domains for which we may handle email. Continue reading “Email Policy”

Transparent Squid Proxy

Over the holidays, I had a user experience and attempted browser hijacking.  It appeared to have bypassed my squid proxy.   My updated configuration now sends all web access via squid.  The old firewall rules, that allowed direct access to the Internet, have been replaced with a transparent Squid proxy.  This runs on my existing Squid Proxy using another port. Continue reading “Transparent Squid Proxy”

Implementing IPv6 6to4 on OpenWRT

As the IPv4 addresses begins to run out I finally invested the time to investigate and implement IPV6. As my ISP has not yet announced availability of IPV6 addresses I chose to implement a 6to4 tunnel. This is simple to implement, and currently well supported. My external firewall is an ASUS wireless router running OpenWRT.  As I have a static IP address, my implementation is simpler than is required by a dynamic address.  Support for dynamic IPv4 addresses is not covered here, but this configuration should work as long as your address does not change.

I initially created a 6to4 implementation without a firewall.  Then to secure my systems I implemented a firewall using Shorewall6-lite.  Until I figured out how to configure the 6tunnel script, I used the command line to bring up the network.  This documentation uses of the 6tunnel script instead of the manual commands.  My configuration does not yet include any IPsec functionality. Continue reading “Implementing IPv6 6to4 on OpenWRT”