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SPF: Ready for Prime Time?
by Pete O'Hara
Introduction
As of the time of this writing in the fight against SPAM a policy has been drafted to target sender address forging called SPF (Sender Policy Framework). The basic premise is to verify that the sender of an email is in fact who they by claim to be. If they are not then mail can be rejected. This could potentially eliminate a big percentage of SPAM and who wouldn't want that.. But there have been problems with SPF and it isn't the big solution that everyone had imagined when it first hit the scene. There are a couple of plaguing issues that keep it from becoming a mature solution with a standard.
What is SPF?
The first version of SPF (also know as "Classic" SPF) was a creation of Meng Wong, founder of Pobox.com. In short the scheme is based on domains publishing what servers are allowed to send mail for themselves using DNS TXT records. A receiving MTA can then look at the domain the sender is claiming to be from and the IP address of the connecting client and check the SPF (DNS TXT) record for that domain and verify if the client is allowed to send mail for the said domain. From the results the receiving MTA can take appropriate actions. The goal is to prevent sender forgery, one of the most common characteristics of spam. SPF was a proposal considered by IETF's MARID group.
Summary
I, as everyone else, would love to be able to block all SPAM and I certainly applaud all of the efforts that have been and are still being made. But it seems obvious that SPF alone isn't going to be the answer. It doesn't handle the forwarding issue and SRS isn't ready as a solution. One could argue that SPF can at least be used not to reject mail but to whitelist mail from senders that pass SPF checks. In view of spammers deploying SPF themselves this would actually be counter productive as it gives them a form of credibility.
Based on the material presented here there are options other than standalone SPF that on the surface seem to provide a better solution but the cost is that they are more complex in that they require reputation/accreditation services. But does the lack of agreement on the simpler SPF (which turned out to be not so simple once the forwarding issues surfaced) foreshadow the difficulties in standardizing more elaborate proposals? If the trend towards reputation/accreditation gains momentum, which by the way would still require some form of sender validation to be established (you can't build a dependable reputation of a sender when it can't be verified), harmony on the architecture of such services seems a very long way off. Sender verification is a problem that certainly needs to be addressed but SMTP wasn't originally designed with this functionality in mind. Therefore a viable solution is not going to be as simple as publishing DNS records of authorized mail servers. SPF on it's own isn't the answer.
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| Fedora | ||
| Fedora Core 3 Update: mikmod-3.1.6-31.FC3 | ||
| 9th, June, 2005
Updated package. advisories/fedora/fedora-core-3-update-mikmod-316-31fc3-10-24-00-119277 |
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| Fedora Core 3 Update: tcpdump-3.8.2-9.FC3 | ||
| 9th, June, 2005
Updated package. advisories/fedora/fedora-core-3-update-tcpdump-382-9fc3-10-24-00-119278 |
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| Fedora Core 3 Update: yum-2.2.1-0.fc3 | ||
| 13th, June, 2005
Updated package. advisories/fedora/fedora-core-3-update-yum-221-0fc3-11-22-00-119303 |
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| Fedora Core 4 Update: elinks-0.10.3-3.1 | ||
| 16th, June, 2005
Updated package. advisories/fedora/fedora-core-4-update-elinks-0103-31-10-19-00-119321 |
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| Fedora Core 4 Update: mikmod-3.1.6-35.FC4 | ||
| 16th, June, 2005
Updated package. advisories/fedora/fedora-core-4-update-mikmod-316-35fc4-10-19-00-119322 |
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| Fedora Core 4 Update: tcpdump-3.8.2-13.FC4 | ||
| 16th, June, 2005
Updated package. advisories/fedora/fedora-core-4-update-tcpdump-382-13fc4-10-20-00-119323 |
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| Fedora Core 4 Update: parted-1.6.22-3.FC4 | ||
| 16th, June, 2005
Updated package. advisories/fedora/fedora-core-4-update-parted-1622-3fc4-11-09-00-119324 |
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| Fedora Core 4 Update: system-config-securitylevel-1.5.8.1-1 | ||
| 16th, June, 2005
Updated package. advisories/fedora/fedora-core-4-update-system-config-securitylevel-1581-1-11-10-00-119325 |
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| Fedora Core 3 Update: checkpolicy-1.17.5-1.2 | ||
| 16th, June, 2005
Updated package. advisories/fedora/fedora-core-3-update-checkpolicy-1175-12-13-59-00-119327 |
||
| Fedora Core 3 Update: selinux-policy-targeted-1.17.30-3.9 | ||
| 16th, June, 2005
Updated package. advisories/fedora/fedora-core-3-update-selinux-policy-targeted-11730-39-13-59-00-119328 |
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| Fedora Core 3 Update: spamassassin-3.0.4-1.fc3 | ||
| 16th, June, 2005
Important update for a Denial of Service vulnerability, plus more bug fixes from upstream. More details available at: https://cwiki.apache.org/confluence/display/SPAMASSASSIN/NextRelease advisories/fedora/fedora-core-3-update-spamassassin-304-1fc3-17-58-00-119332 |
||
| Fedora Core 4 Update: spamassassin-3.0.4-1.fc4 | ||
| 16th, June, 2005
Important update for a Denial of Service vulnerability, plus more bug fixes from upstream. More details available at: https://cwiki.apache.org/confluence/display/SPAMASSASSIN/NextRelease advisories/fedora/fedora-core-4-update-spamassassin-304-1fc4-17-59-00-119333 |
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| Fedora Core 3 Update: gaim-1.3.1-0.fc3 | ||
| 16th, June, 2005
More bug and denial of service fixes. advisories/fedora/fedora-core-3-update-gaim-131-0fc3-17-59-00-119334 |
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| Fedora Core 4 Update: gaim-1.3.1-0.fc4 | ||
| 16th, June, 2005
More bug and denial of service fixes. advisories/fedora/fedora-core-4-update-gaim-131-0fc4-18-00-00-119335 |
||
| Gentoo | ||
| Gentoo: libextractor Multiple overflow vulnerabilities | ||
| 9th, June, 2005
libextractor is affected by several overflow vulnerabilities in the PDF, Real and PNG extractors, making it vulnerable to execution of arbitrary code. |
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| Gentoo: Ettercap Format string vulnerability | ||
| 11th, June, 2005
A format string vulnerability in Ettercap could allow a remote attacker to execute arbitrary code. |
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| Gentoo: GNU shtool, ocaml-mysql Insecure temporary file | ||
| 11th, June, 2005
GNU shtool and ocaml-mysql are vulnerable to symlink attacks, potentially allowing a local user to overwrite arbitrary files. |
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| Gentoo: gedit Format string vulnerability | ||
| 11th, June, 2005
gedit suffers from a format string vulnerability that could allow arbitrary code execution. |
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| Gentoo: GNU shtool, ocaml-mysql Insecure temporary file | ||
| 11th, June, 2005
GNU shtool and ocaml-mysql are vulnerable to symlink attacks, potentially allowing a local user to overwrite arbitrary files. |
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| Gentoo: LutelWall Insecure temporary file creation | ||
| 11th, June, 2005
LutelWall is vulnerable to symlink attacks, potentially allowing a local user to overwrite arbitrary files. |
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| Gentoo: Ettercap Format string vulnerability | ||
| 11th, June, 2005
A format string vulnerability in Ettercap could allow a remote attacker to execute arbitrary code. |
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| Gentoo: Gaim Denial of Service vulnerabilities | ||
| 12th, June, 2005
Gaim contains two remote Denial of Service vulnerabilities. |
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| Gentoo: TCPDump Decoding routines Denial of Service | ||
| 13th, June, 2005
While working on the tcpdump issues solved in the original version of this GLSA, Simon L. Nielsen from FreeBSD Security Team discovered a similar infinite loop DoS vulnerability in the BGP handling code (CAN-2005-1267). |
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| Gentoo: MediaWiki Cross-site scripting vulnerability | ||
| 13th, June, 2005
MediaWiki is vulnerable to a cross-site scripting attack that could allow arbitrary scripting code execution. |
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| Red Hat | ||
| RedHat: Low: gzip security update | ||
| 13th, June, 2005
An updated gzip package is now available. This update has been rated as having low security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-low-gzip-security-update-RHSA-2005-357-01 |
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| RedHat: Moderate: gftp security update | ||
| 13th, June, 2005
An updated gFTP package that fixes a directory traversal issue is now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-moderate-gftp-security-update-RHSA-2005-410-01 |
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| RedHat: Low: squid security update | ||
| 13th, June, 2005
An updated squid package that fixes several security issues is now available. This update has been rated as having low security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-low-squid-security-update-75129 |
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| RedHat: Low: rsh security update | ||
| 13th, June, 2005
Updated rsh packages that fix a theoretical security issue are now available. This update has been rated as having low security impact by the Red Hat Security Response Team advisories/red-hat/redhat-low-rsh-security-update-25924 |
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| RedHat: Moderate: gedit security update | ||
| 13th, June, 2005
An updated gedit package that fixes a file name format string vulnerability is now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team advisories/red-hat/redhat-moderate-gedit-security-update-RHSA-2005-499-01 |
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| RedHat: Moderate: sysreport security update | ||
| 13th, June, 2005
An updated sysreport package that fixes an information disclosure flaw is now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team advisories/red-hat/redhat-moderate-sysreport-security-update-RHSA-2005-502-01 |
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| RedHat: Low: tcpdump security update | ||
| 13th, June, 2005
Updated tcpdump packages that fix a security issue are now available. This update has been rated as having low security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-low-tcpdump-security-update-RHSA-2005-505-01 |
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| RedHat: Low: mikmod security update | ||
| 13th, June, 2005
Updated mikmod packages that fix a security issue are now available. This update has been rated as having low security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-low-mikmod-security-update-RHSA-2005-506-01 |
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| RedHat: Low: squid security update | ||
| 14th, June, 2005
An updated squid package that fixes several security issues is now available. This update has been rated as having low security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-low-squid-security-update-75129 |
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| RedHat: Moderate: telnet security update | ||
| 14th, June, 2005
Updated telnet packages that fix an information disclosure issue are now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-moderate-telnet-security-update-RHSA-2005-504-00 |
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| RedHat: Low: bzip2 security update | ||
| 16th, June, 2005
Updated bzip2 packages that fix multiple issues are now available. This update has been rated as having low security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-low-bzip2-security-update-RHSA-2005-474-01 |
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| RedHat: Moderate: mc security update | ||
| 16th, June, 2005
Updated mc packages that fix several security issues are now available for Red Hat Enterprise Linux 2.1. This update has been rated as having moderate security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-moderate-mc-security-update-66451 |
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| RedHat: Moderate: gaim security update | ||
| 16th, June, 2005
An updated gaim package that fixes two denial of service issues is now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team. advisories/red-hat/redhat-moderate-gaim-security-update-RHSA-2005-518-01 |
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