SpamC rules signification

MailCleaner Support
Added 13 days ago

If an email was caught by SpamC, you may want to know what does a rulename mean. This document lists the rules our users ask for the most commonly, this is not and doesnt aim to be a complete list of the rules we are using.

Here is how to handle SpamC rules in MailCleaner :

https://support.mailcleaner.net/boards/3/topics/51-how-to-create-custom-spamc-rules


RCVD_IN_SORBS_SPAM 2.0
SORBS is a RBL we provide for administrators who want an agressive filtering. You can uncheck it from SpamC if you see it present in several false positives reports.

BOTNET_BADDNS
is a rule relative to the DNS configuration of a server. This is a meta tule including a lot of different elements

SUBJ_ALL_CAPS
The mail subject is entirely in caps

RDNS_DYNAMIC
The full circle name used by the sending server is dynamic

RDNS_NONE
MailCleaner checks that the sending server is using a "Full Circle DNS" name (This can be checked here : http://multirbl.valli.org/fcrdns-test/ )

BOTNET_CLIENT
This rule adds points when several rule of BOTNET have been met

MC_URI_EASYMONEY_LVL4
MailCleaner s rule : Message contains a sentence like "claim your free copy" or "Check secret story". This rule detects sentences done with this pattern "one of the words(claim see check) + your + one of the word(free full secret) + one of the word (copy story)"

DYN_RDNS_AND_INLINE_IMAGE
The mail contains an image attachment, and the message was received by the last trusted relay from an IP address with a reverse DNS name that suggests it is dynamically allocated.

DC_IMAGE_SPAM_HTML
The mail has at least one large image attachment and a comparatively small amount of text.

DKIM_VALID_AU
Message has a valid DKIM or DK signature from author's domain

BOTNET_IPINHOSTNAME
Hostname contains a subpart of its own IP address

BOTNET_CLIENTWORDS
the sending server hostname contains strings leading to think the mail was sent by an email client instead of a real mail server

MPART_ALT_DIFF
The mail contains alternative parts which are supposed to be identical so that the same text is displayed in text or HTML mode. Here the 2 parts are different, this is most of the time a spam technique

DC_IMAGE_SPAM_TEXT
Possible Image-only spam with little text

MC_CONTAINS_ZERO1
Message contains an invisible character usually used to prevent antispam to correctly identified a word

DC_PNG_MULTI_LARGO 0.7
Message has 2+ inline png covering lots of area

HTML_IMAGE_RATIO_04 0.6
This may indicate a message using an image instead of words in order to sidestep text-based filtering

DC_IMG_HTML_RATIO 0.3
Low body to pixel area ratio

DC_IMG_TEXT_RATIO
Low body to pixel area ratio

MC_CONTAINS_ZERO1
is a rule which detects the use of specific character. This one will not be displayed in the message , spammers use it to circumvant some rules detections for example viagra would be detected but using this character in the word viagra would let it be displayed normally but would prevent it to be detected (as it would be written "via​gra" and not "viagra")

SARE_ADLTSUB10
mail subject contains a (maybe obfuscated) string based on the rape word --Since this may involve obfuscating techniques, it is sometime hard to find out what lured SpamC

DEAR_SOMETHING
This detects subjects / mail beginning like "Dear Mister". This is rarely used in ham and corresponds to specific spams waves

DKIM_ADSP_ALL
The sender's domain says that it uses DKIM on all email, but no valid signature was found. That suggests that the message might not have originated with the purported sender.

DKIM_SIGNED
Message has a DKIM or DK signature, not necessarily valid

SINGLE_HEADER_1K
SINGLE_HEADER_2K
SINGLE_HEADER_3K
SINGLE_HEADER_4K
SINGLE_HEADER_5K
Headers contain between xK and (x+1)K characters total

MIME_HEADER_CTYPE_ONLY
The mail is malformed : the specified Content-type for the mail is something other than "text/plain", so the headers should have conformed to the MIME specification. This suggests that the message was generated by a badly-written mailout program rather than by a normal email client.

SUBJ_ILLEGAL_CHARS
The Subject header contains 8-bit and other illegal characters that should be MIME encoded, as described in RFC 2045

TVD_SPACE_RATIO_MINFP
this is about the ratio of spaces to non-spaces in each paragraph. apparently messages where generally there are lots of spaces mean the message is spam.

PHP_ORIG_SCRIPT
identifies the email came from a PHP script

SUBJECT_NEEDS_ENCODING
The Subject: header line contains characters outside of the US-ASCII range that have not been encoded with Base64 or Quoted-Printable encoding. This violates the RFC standards for mail headers. Properly behaved MUAs would be expected not to do this

MISSING_DATE
The date header is missing.

FUZZY_XPILL
The message contains the name of a pharmatical product written in an obfuscated way

MISSING_MID
mail doesnt contain a message-ID header

AXB_X_FF_SEZ_S
This rules applies when there is an header X-Forefront-Antispam-Report in a mail. Here you can have more information on why this header was added, see https://technet.microsoft.com/en-us/library/dn205071(v=exchg.150).aspx