An online marketplace has 400 attempts at DDoS attacks in 3 years, five of which take the website down for an average of 1 day. If the value of the whole website is one million pounds per year, what is the exposure factor for the website for going down for one day in a year?
Exposure Factor
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Dr.Peterson
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Changing the question from homework to a challenge to others doesn't absolve you of the need to show your work. Please read our submission guidelines. Note in particular that this is not just a math question; it requires defining the terms, such as "exposure factor", in the problem domain. That may be why you didn't get any answers before. We're happy to help you with the math if you do your part!
Dr.Peterson
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Not exactly pejorative, and I didn't take it as such. Wikipedia says:
Google says, "a person with knowledge or a skill considered to be complex, arcane, and difficult."
My objection, if any, is to the implication that our motivation is to show off our skills, and that that could trick us into violating our purposes.
Boffin is a British slang term for a scientist, engineer, or other person engaged in technical or scientific research and development. A "boffin" was generally viewed by the regular services as odd, quirky or peculiar, though quite bright and essential to helping in the war effort. The World War II conception of boffins as war-winning researchers lends the term a more positive connotation than related terms such as nerd, egghead, geek or spod.
Google says, "a person with knowledge or a skill considered to be complex, arcane, and difficult."
My objection, if any, is to the implication that our motivation is to show off our skills, and that that could trick us into violating our purposes.
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Haha...I've had students online say something like "If you're unable to solve this problem, just say so...it's okay..." when I've prodded them to show some effort and actually take part in solving the problem...as if being "called out" is going to make me solve the problem to "defend my honor" and demonstrate I can in fact solve the problem, like I'm brand new at this or something. 
HallsofIvy
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I recognized "boffin" (personally, I don't spend as much time "boffing" as I would like) but "spod" was new to me.
Wow! I didn't realise that the word boffin would have such an impact......it was meant in the friendly sense, not to give any sleight or offence.
To more fully frame the problem, I have endeavoured to use the vast resources of the internet to answer this question but have not found anything that explicitly answers what I am looking for. The Exposure Factor I understand is:
Exposure Factor = ( Frequency x Exposure Duration ) / Averaging Time, or
EF = F x ED / AT
Clear enough so far. The frequency of the the system failing I think is 5 times in 3 years or 5/3 per year. The Exposure Duration I see as one year and call it 1 year. The Averaging Time therefore I think should be 1 year x 365 days / year or
EF = ( (5/3) x 1 ) / 365 or
EF = 1 / 219
so EF = 0.004566
Intuitively it feels right as it should be a very small number but it is not the correct answer I understand. I am concerned that I am not using the right time intervals for ED and AT but, as I have said, nothing I have found on the internet nor in YouTube helps.
There has got to be someone out there who understands this equation!
To more fully frame the problem, I have endeavoured to use the vast resources of the internet to answer this question but have not found anything that explicitly answers what I am looking for. The Exposure Factor I understand is:
Exposure Factor = ( Frequency x Exposure Duration ) / Averaging Time, or
EF = F x ED / AT
Clear enough so far. The frequency of the the system failing I think is 5 times in 3 years or 5/3 per year. The Exposure Duration I see as one year and call it 1 year. The Averaging Time therefore I think should be 1 year x 365 days / year or
EF = ( (5/3) x 1 ) / 365 or
EF = 1 / 219
so EF = 0.004566
Intuitively it feels right as it should be a very small number but it is not the correct answer I understand. I am concerned that I am not using the right time intervals for ED and AT but, as I have said, nothing I have found on the internet nor in YouTube helps.
There has got to be someone out there who understands this equation!
Dr.Peterson
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I've looked for information about these concepts, and haven't found any source that uses "exposure factor" in the same way. Maybe you need to tell us the definitions given for all the terms involved in your formula; if you can give us a URL or an image of your source, that might help even more.
If EF means the empirical probability of an event happening, I would consider it to be 5/(3*365), the ratio of events that occurred to total number of opportunities (days). That gives the same number you got.
But that raises another question. You say, "it is not the correct answer I understand." How do you know that? Is this a question on some site that only tells you if your answer is wrong? Are you sure you trust it? Is any explanation given, or an example?
If EF means the empirical probability of an event happening, I would consider it to be 5/(3*365), the ratio of events that occurred to total number of opportunities (days). That gives the same number you got.
But that raises another question. You say, "it is not the correct answer I understand." How do you know that? Is this a question on some site that only tells you if your answer is wrong? Are you sure you trust it? Is any explanation given, or an example?
Dr.Peterson
Thank you very much for your prompt and considered response here. A friend of mine's son has a maths problem he is stuck on and as I have a background in maths, I said I'd see what I could do. Not having found reference to this material in any text book I have nor on the internet including seeing a worked example someone has done on YouTube nor even Wikipedia, I have not been able to supply him with an answer that is "right".
Your last paragraph is spot on insomuch as the "answer" is to be entered into a website and depending on whether the answer is the same as the website, it is either right or wrong. Clearly wrong does not necessarily mean the answer we have both derived is wrong......
He does not have any formulae to work from other than a scribbled note with the EF = F x ED / AT formula. This I have found on various sites (usually associated with medical science) but a detailed, explicit, exact, unambiguous explanation I have not found. As the EF you would hope is pretty straightforward to determine, it begs the question how do you define the other two terms? There can only be so many possible answers of course but the point of the question is to be able to apply the formula to a real-life problem, not fiddle the answer to get a "correct" response from the machine. I had assumed there was a mistake in defining the time interval but if you write down the "year" and "per year" etc in the formula, these cancel and I've ended up with the same number through two different routes.
Thank you for your efforts. I assumed I was barking up the wrong tree on this and had missed something obvious. Still, maybe we have?
There has to be a YouTube video here somewhere........if only we could get it to "work"!
Thank you again.
Regards
4J
Thank you very much for your prompt and considered response here. A friend of mine's son has a maths problem he is stuck on and as I have a background in maths, I said I'd see what I could do. Not having found reference to this material in any text book I have nor on the internet including seeing a worked example someone has done on YouTube nor even Wikipedia, I have not been able to supply him with an answer that is "right".
Your last paragraph is spot on insomuch as the "answer" is to be entered into a website and depending on whether the answer is the same as the website, it is either right or wrong. Clearly wrong does not necessarily mean the answer we have both derived is wrong......
He does not have any formulae to work from other than a scribbled note with the EF = F x ED / AT formula. This I have found on various sites (usually associated with medical science) but a detailed, explicit, exact, unambiguous explanation I have not found. As the EF you would hope is pretty straightforward to determine, it begs the question how do you define the other two terms? There can only be so many possible answers of course but the point of the question is to be able to apply the formula to a real-life problem, not fiddle the answer to get a "correct" response from the machine. I had assumed there was a mistake in defining the time interval but if you write down the "year" and "per year" etc in the formula, these cancel and I've ended up with the same number through two different routes.
Thank you for your efforts. I assumed I was barking up the wrong tree on this and had missed something obvious. Still, maybe we have?
There has to be a YouTube video here somewhere........if only we could get it to "work"!
Thank you again.
Regards
4J
Dr.Peterson
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It would have been helpful if you had told us the whole story from the start, as we ask in our submission guidelines (which nobody seems to read and follow). Bare problems are not a good way to get started; context can work wonders.
Now you have to do the same thing we have to do: chase down the information this boy is withholding from you! If this is for a class, he must have been taught something about it. If it is not in his textbook or class notes, then maybe he wasn't paying attention somewhere. If he were asking me for help in person, I would quickly have my hands on whatever material he had brought with him to look for relevant information; that includes the website (many of which have a button to show examples or other information, which many students have never even noticed).
But in addition to that information you can request, there's a little more that you may already know. Do you have an idea what course he is taking and what topics he has been learning? How old is he? Also, are there any specific instructions with the question, such as how many decimal places they want, or a specific form such as a simplified fraction or a percentage? When I help a student with a computer problem like this, that's one of the first things I look for; I tell them to always check "the blue letters", since such instructions are often in blue on their site.
Now you have to do the same thing we have to do: chase down the information this boy is withholding from you! If this is for a class, he must have been taught something about it. If it is not in his textbook or class notes, then maybe he wasn't paying attention somewhere. If he were asking me for help in person, I would quickly have my hands on whatever material he had brought with him to look for relevant information; that includes the website (many of which have a button to show examples or other information, which many students have never even noticed).
But in addition to that information you can request, there's a little more that you may already know. Do you have an idea what course he is taking and what topics he has been learning? How old is he? Also, are there any specific instructions with the question, such as how many decimal places they want, or a specific form such as a simplified fraction or a percentage? When I help a student with a computer problem like this, that's one of the first things I look for; I tell them to always check "the blue letters", since such instructions are often in blue on their site.
The course he attends which I have to be careful not to name or allude to is sparse with their material both presented in class and hand-outs and I agree that it wrong but until something changes that is the way it is. This problem is not the only one that has required imagination to solve and probably won't be the last. It has been the most intractable problem as it does not seem that anyone has applied this formula to this type of problem AND posted it online and no textbooks that I have seen deal with this. There probably are but this is a finite world in terms of time and money.
Maybe we have answered the problem correctly and the "answer" in the system is wrong - it wouldn't be the first time.
Thank you for your efforts.
Maybe we have answered the problem correctly and the "answer" in the system is wrong - it wouldn't be the first time.
Thank you for your efforts.
Dr.Peterson
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Of course, a problem that doesn't define its terms is not merely intractable; it is an invalid problem. Undefined questions don't have answers.
Genius4Dayz
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You are over complicating the answer. You just need one day of 365 as a percent and convert that to decimal