In a similar vein, over the past few years whenever I've got in a discussion with IT people who defend mandatory password change policies, I ask them to give me the last password they were using before changing it. No one has ever taken me up on that.
However, I would also not defend mandatory password change policies, so you would never end up asking me :D
† I can't tell you now because the day after I ceased working for them I sent the nice leather-bound book I write passwords down in to my Product Owner, so that the answer to all subsequent "Do you happen to remember the password for...?" questions would be "Either it's in the book which you have or No". To be fair he only called me and asked that question once, which is why he was my favourite Product Owner, "capacity to learn from experience: 10/10".
If something got a look inside your book, everything is compromised. At least by changing to another random gibberish password, an attacker would not get back in (in contrast to someone that increments a number, for example), but how much damage can something do in that time before you notice? How long do you think it takes a skilled attacker to install a backdoor (the answer is definitely less than 44 days)?
This is the second major problem with password rotation: it is false security. If credentials are compromised, immediately change them: don't wait 45 or 90 days.
If they're not compromised, changing them is basically pointless, because humans are going to human and either have an incrementing number, predictable pattern, or actual complex, random, unrelated passwords ... that they then write down.
Writing passwords down on paper and leaving that paper in an insecure area isn't.
Your little address book full of passwords is the same as a password manager, and for a lot of people it's easier for them to manage the security of a booklet than it is to handle a password manager properly. And for those people, it's definitely worth using a book for the sake reasons we say using a password manager is a good idea
I used a book for passwords issued by that employer because at that time they lacked any in-house password manager and I foresaw from the outset that I would want to be able to hand them "my passwords" in the limited context of that employment as distinct from stuff like my personal Wikipedia account, my Google account and so on.
Personally I would be much more concerned about other things - my stuff is there, not to mention often myself - but I'm sure that a vast faceless corporation would be primarily concerned with the potential for these hypothetical bad guys to learn and maybe disseminate secret passwords.
How often do you think that actually happens? It's a bit... high risk for opportunistic "cyber criminals" don't you think? Figure out where key employees live, then break in and... look for passwords they've written down and then presumably use them quickly before they're invalidated.
Besides, actually remembering your passwords is a security flaw, too. Memorable passwords are naturally less random, and if the password is in my mental memory, an attacker can compromise my password by smashing me over the kneecap with a heavy wrench until I tell them. If I don’t even know my password, that’s probably bad news for my kneecaps but slightly more secure overall.
If someone did break into my house as an act of espionage (corporate or nation state), I'd be worried about much more than just my password security.
In my experience the average password consists of 1-3 words with some meaning to the user, sometimes either in 1337speak or followed by numbers/symbols if the password policy requires them.
Attackers don't need hints on passwords, they don't need hints on targets. They just target everyone, and try all easy passwords.
Pentester here, to clear any dubious assumptions.
4-5 dictionary words with proper sentence structure is a lot safer for the most part. Random safer still, but much harder to remember... my current password for work in a sentence with 24 characters. spaces, capitals and punctuation. Other than my OS and password manager, I really don't remember any other passwords I use, and the majority are random generated at this point.
I also use a wildcard mail forwarder, so most new sites I've used in the past year or two are all unique emails as well.
Dictionary word with first letter uppercase, followed by two-digit number, followed by exclamation mark. With the overall length exactly being the minimum length of the policy.
I simply disabled password rotation policy on my account ノ(ジ)ー'
I used to do a lot of contract work for the Clarke County School District in Athens, GA. For "security" reasons they weren't able to create domain accounts for people who weren't full time employees, so I'd often have to track down the IT manager to gain access to servers I was working on.
He eventually got sick of having to drop what he was doing a dozen times a day, so one day he just gave me his password: a dictionary word followed by the number 23. Eventually the password failed, and he gave me his new password: that same dictionary word followed by a 24.
Fast forward a few years and I'm back installing some updates, and before I get to work he hands me a slip of paper, on which he had written Dictionaryword29.