What is Server Message Block (SMB) and Why is it SO Vulnerable?
People who work in cybersecurity know that the Server Message Block (SMB) is something that had a lot of vulnerabilities associated with it. But, just what is SMB? This blog post was taken from a Medium article that I published back in mid-2024.
William Heldman, Ph.D.
1/11/20243 min read


The Server Message Block (SMB) protocol has been around a long, long time. And it has gone through updates over the years, mostly because lots of vulnerabilities have been exploited in this protocol.History
In the 1980s the SMB protocol was initially developed by IBM for their PC LAN networking system. I remember the days of IBM PS/2 PCs (proprietary as heck), and token ring networking (yay MAUs!)
Back in those days, you had a computer running the Disk Operating System (DOS), and, while there were knock-offs, the two big players were IBM PC-DOS, and Microsoft’s MS-DOS. (Those of you who worked with DOS back in the day might also fondly remember a product called Dr DOS — or DR-DOS as well.) DOS consisted of a black screen with white lettering, and you could only run one application at a time.
Bill Gates’ company Microsoft had been hired by IBM to work on the DOS operating system. However, tensions arose due to IBM’s ongoing development work on a windowed OS called OS/2, and Microsoft’s own ventures into what would one day become Microsoft Windows. There was a splitting of the sheets, and Gates went his way and sold scads of copies of MS-DOS, while IBM, well, not so much.
You might be able to argue who had the better version of DOS, but you can’t argue who the clear winner was in the DOS wars. It was all about Microsoft at that point.
This is kind of a sad legacy of IBM’s. It seems as though every time they get something successful going in the PC market, they divest themselves of it. They had a good thing going with PS/2 computers until the whole “IBM clone” phenomenon hit consumers. Manufacturers started coming out with PCs that would run DOS, but getting other software to run could be problematic. Vendors began saying their software was “IBM PS/2 or IBM clone-compatible” and that was what got the ball rolling toward moving away from expensive PS/2 computers into less expensive clones. That didn’t mean that if you had a clone certain software products would run on it, but the clones took off nonetheless.
Moreover (and I’m editorializing a bit here), IBM also had a darn good product in their ThinkPad laptops and wound up divesting the entire operation to Lenovo. IBM won PC Magazine’s Editor’s Choice one year for their ThinkPad laptops. I guess I’ll never understand why they divested themselves of it, or maybe they didn’t — maybe Lenovo is an IBM division? I’m not sure. But I like Lenovo computers and I use them.
Truth be told, OS/2 was a pretty darn cool OS. I can remember having to install OS/2 on a computer in Boulder so that it could talk to another computer in Japan using Microsoft MS-Mail (an early Microsoft email program). At the time (1994), Microsoft’s server software didn’t have the technical depth to set up such a connection, whereas OS/2 had the depth of IBM’s years of technical research. It was painful getting everything set up, but super cool when our salespeople from Tokyo could send an email to our folks in Boulder, and vice-versa.
IBM tried to resurrect OS/2 with a nifty new little version they called OS/2 Warp. There were awesome television commercials, glitzy marketing campaigns; but, sadly, Microsoft had carved out a humongous niche for itself and IBM simply could not (or would not) keep up. The link below is an actual IBM PS/2 Warp TV commercial.
As I write about OS/2, I’m reminded of Steven Jobs’ efforts in the arena of developing a computer that had a GUI, as opposed to black and white command line DOS. The computer was called NeXT. As I recall, it was only sold in college bookstores, and it was super expensive. Because I didn’t own one, I’m not sure if there were apps for it, but it never did sell well, and Jobs finally wound up pulling the plug on the product.
And, I really need to say that, while Microsoft has released some super good operating systems over the years, there was one that was a super-clunker (I’m not talking about Windows Vista here). It was called — I’m not making this up — Microsoft Bob. It tried to use the metaphor of a living room in a house where all your stuff was stored. I believe you can still buy a shrink-wrapped copy of Microsoft Bob from E-Bay.
You can read more on my Medium page. Enjoy!!