3CX DLL-Sideloading attack: What you need to know
I have seen the other posts about the Spam engine since V9.706, but found no satisfying solution.
I have checked all recommended hints. So the first check for the hardware:
loginuser@fw:/home/login > grep flags -m1 /proc/cpuinfo
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave rdrand lahf_lm abm 3dnowprefetch arat epb xsaveopt pln pts dtherm tpr_shadow vnmi flexpriority ept vpid fsgsbase tsc_adjust erms invpcid rdseed smap
So the hardware seems to be OK.
Then I checked for all recommended RBLs:
Next I checked the recognition rate for the last months:
June 2021:
July 2021:
So the spam recognition rate sank from 695 to 125 with nearly the same amount of tested mails.
So I installed SpamAssassine on my mail server and got a lot of indicated spam. An example of today:
Return-Path: <unsubscribe@09.win.cinmass.com>X-Original-To: xxxDelivered-To: xxx...from <unsubscribe@09.win.cinmass.com>; Thu, 19 Aug 2021 22:06:04 +0200X-SASI-Hits: BODYTEXTH_SIZE_10000_LESS 0.000000, BODYTEXTP_SIZE_3000_LESS 0.000000, BODY_SIZE_4000_4999 0.000000, BODY_SIZE_5000_LESS 0.000000, BODY_SIZE_7000_LESS 0.000000, DATE_TZ_NA 0.000000, HREF_LABEL_TEXT_NO_URI 0.000000, HREF_LABEL_TEXT_ONLY 0.000000, HTML_NO_HTTP 0.100000, NO_CTA_URI_FOUND 0.000000, NO_MESSAGE_ID 0.299999, NO_URI_HTTPS 0.000000, REPLYTO_FROM_DIFF_ADDY 0.100000, SENDER_NO_AUTH 0.000000, SUPERLONG_LINE 0.050000, UTF8_SUBJ_OBFU 0.100000, __ANY_URI 0.000000, __BODY_TEXT_X4 0.000000, __CT 0.000000, __CTYPE_HAS_BOUNDARY 0.000000, __CTYPE_MULTIPART 0.000000, __CTYPE_MULTIPART_ALT 0.000000, __DATING_PHRASE 0.000000, __FRAUD_BODY_WEBMAIL 0.000000, __FRAUD_CONTACT_ADDY 0.000000, __FRAUD_INTRO 0.000000, __FRAUD_MONEY 0.000000, __FRAUD_MONEY_BIG_COIN 0.000000, __FRAUD_MONEY_BIG_COIN_GER 0.000000, __FRAUD_MONEY_CURRENCY 0.000000, __FRAUD_MONEY_CURRENCY_DOLLAR 0.000000, __FRAUD_MONEY_VALUE 0.000000, __FRAUD_WEBMAIL 0.000000, __FROM_DOMAIN_NOT_IN_BODY 0.000000, __FROM_NAME_NOT_IN_ADDR 0.000000, __HAS_FROM 0.000000, __HAS_HTML 0.000000, __HAS_REPLYTO 0.000000, __HEADER_ORDER_FROM 0.000000, __HREF_LABEL_TEXT 0.000000, __HTML_AHREF_TAG 0.000000, __HTML_HREF_TAG_X2 0.000000, __MIME_HTML 0.000000, __MIME_TEXT_H 0.000000, __MIME_TEXT_H1 0.000000, __MIME_TEXT_H2 0.000000, __MIME_TEXT_P 0.000000, __MIME_TEXT_P1 0.000000, __MIME_TEXT_P2 0.000000, __MIME_VERSION 0.000000, __MSGID_DOMAIN_NOT_IN_HDRS 0.000000, __PHISH_SPEAR_ACCOUNT_1 0.000000, __PHISH_SPEAR_GREETING 0.000000, __RCPT_DOMAIN_NOT_TO 0.000000, __REPLYTO_SAMEAS_FROM_DOMAIN 0.000000, __RUS_HASHBUSTER_1251 0.000000, __SPAM_FLAG_YES 0.000000, __SUBJ_ALPHA_END 0.000000, __SUBJ_ALPHA_END2 0.000000, __SUBJ_HIGHBIT 0.000000, __TAG_EXISTS_HTML 0.000000, __TO_MALFORMED_2 0.000000, __TO_NO_NAME 0.000000, __URI_MAILTO 0.000000, __URI_NO_WWW 0.000000, __URI_NS 0.000000, __UTF8_SUBJ 0.000000X-SASI-Probability: 10%X-SASI-RCODE: 200X-SASI-Version: Antispam-Engine: 4.1.4, AntispamData: 2021.8.19.193316X-MailCleaner-SPF: passContent-Type: multipart/alternative; boundary="===============1088584699=="MIME-Version: 1.0Subject: [***** SPAM 7.3 *****] =?utf-8?q?Gl=C3=BCckw=C3=BCnsche_an_xxx_?=To: xxxFrom: "Donald Lewis" <unsubscribe@09.win.cinmass.com>Date: Thu, 19 Aug 2021 13:06:03 -0700Reply-To: subscribe@09.win.cinmass.comX-Spam-Flag: YESX-Spam-Status: Yes, score=7.3 required=5.0 tests=HTML_MESSAGE,LOTS_OF_MONEY, MISSING_MID,RCVD_IN_SBL,RCVD_IN_SBL_CSS,SPF_HELO_NONE,SPF_SOFTFAIL, UNPARSEABLE_RELAY autolearn=no autolearn_force=no version=3.4.4X-Spam-Report: * 3.6 RCVD_IN_SBL_CSS RBL: Received via a relay in Spamhaus SBL-CSS * [188.165.148.172 listed in zen.spamhaus.org] * 2.6 RCVD_IN_SBL RBL: Received via a relay in Spamhaus SBL * [82.165.159.37 listed in zen.spamhaus.org] * 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record * 1.0 SPF_SOFTFAIL SPF: sender does not match SPF record (softfail) * 0.0 HTML_MESSAGE BODY: HTML included in message * 0.0 LOTS_OF_MONEY Huge... sums of money * 0.1 MISSING_MID Missing Message-Id: header * 0.0 UNPARSEABLE_RELAY Informational: message has unparseable relay * linesX-Spam-Level: *******X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on uhs20You will not see this in a MIME-aware mail reader.
So SpamAssassine scores the mail for beeing listed at zen.spamhouse.org and others with 7.3 but the Sophos UTM SASI shows 10% Probability and let the mail pass.
Another observation is that nearly all recognized spam came via SMTP. The POP-Accounts are now filtered very rare.
What else information can I give for a solution?
Hi wk,
Thank you for reaching out to the Community!
Did you open a support case with original spam sample emails? If not, I'd suggest doing that and submit the sample spam samples to Sophos LAB for investigation.
Thanks,
I'm on a home licence here.
Since I am retired no more partner status.
cuWalter
Harsh, this looks like something the devs would want to see. Walter, if you aren't contacted next week by Sophos concerning your work with SASI, PM me and I'll open a case with Support.
Cheers - Bob