Got an invoice in the mail this morning. A company I never heard of, with this message:

Here is your bill.

Waiting for your answer

Risus Incorporated
Lev Mckenzie
(896) 756-0588

The attachment is named “Risus Incorporated.bill42zo.06.p24me38i.rtf”.

So what’s wrong with that?

• I have no business relationship with any of those names.
• The company name doesn’t match the email domain.
• 896 is a fake area code.
• That last name is odd–that ‘k’ in ‘Mckenzie’ should be capitalized. Who misspells their own name?
• The web site matching the email address that appears to have sent the email is the “Arab Real Estate Company”, with what appears to be a legit web site in Arabic.
• The “invoice” is a RTF file, also known as a “Rich Text File”; that’s what we programmers used to use to create help files, so it is very capable of holding scripts and program code, but it’s a horrible choice for sending an actual invoice.

So it’s an obvious fake: a phish, an attempt to get me to open something I shouldn’t. OK, with caution, I looked inside. (Don’t do what I do. I’m a professional, and I don’t just double-click to see if anything explodes.) Inside there are multiple pages of this:

 

valvular wishbone sallymen poop gyn underdepth fearfulness feistiest vapulate gigsmen hemagglutinate bridoon diactinism shiplet subintegumental marliest vagabonding proamateur atamasco supracargo teleplay spherify rhytidome unheart verifiably neobotany horizontalism presbyterianism fatigues reconsign ower incontrollable gangliglions externa allopathically creep witches cicatrices scrappiest hardfistedness harakiri subcortically privily sappily intendence nearshore hypereutectoid chylidrosis metosteal sarcasm's dropsied earthing devour patashte stereoelectric brattie counterprove adventure resprout hyperparasitize humanised unevil pinyin prerighteousness pidgized shellful recompute ultrafiltration masslessness spig expectance voidance multipartisan fin mandrin mezair wastes audiotapes contrariness nonrefractional abnormalise wrihte morphonemics splenetive utilize goniostat chondrocranium

Well, that’s just a paste of words, mostly from a scientific dictionary, in random order, probably chosen because scientific terms are basically international, and would not trigger a “Wrong language” alert in an automated scan.

After a lot of that, I can see function calls to Windows libraries. In other words, yes, it’s a program or a script. Beyond that, I leave it to the malware labs, and yes, I sent a copy to one of the top providers, and they will share it with the other anti-malware companies.

FAIL

And here’s the issue. The computer that this arrived on has in excess of 12 layers of security filtering, between software, settings, and plugins that block evil activity, and is 100% up-to-date, confirmed with three different products. The message wasn’t flagged by Clam Antivirus on the mail server. And on arrival, I saved the attachment, and manually scanned it with three anti-virus and anti-malware products.

There were NO ALERTS AT ALL. Why? Because these anti-malware products are based on a spell checker. They do a mathematical calculation of the contents of a known-evil sample, and come up with a long number that identifies exactly that file, and they save that and send it out to all the computers running that AV product. Takes three days from submission to prevention. But this sample is full of dictionary words. Well, if the malware authors are generating new random pages of word scrambles in each attached RTF file, not one of their “invoices” will ever be detected. EPIC FAIL. Even if they don’t send you a dictionary, there’s a three-day lag time, and until then, the malware is undetectable.

The Fix

• Educate your users.
• Don’t open suspicious attachments.
• Keep your patches up-to-date. Automate it, so that published security holes used by the bad guys aren’t available on your systems.
• Use ONLY non-Administrator accounts on your computers.
• Uninstall software that connects to the internet when it’s no longer needed, to reduce attack surface and reduce needed patches.

So there’s no infection here. I didn’t open the invoice. I don’t owe money to a real estate company in Saudi Arabia. Deleted. And you don’t need software to tell you when an email is just plain impossibly wrong.