本文探讨了声音数字化的过程，解释了数字数据为何更能抵抗噪声干扰，并介绍了JPEG图像压缩格式的特点。此外，还讨论了视频压缩格式h.264，展示了如何使用电子表格计算个人步数的总和及平均值，并强调了密码强度的重要性。最后，文中详细讲解了网络钓鱼攻击与防范措施，以及如何识别并避免特洛伊木马式的电子邮件攻击。
Week 6 > Analog and Digital 2 Exercises > Vertical
Q1: Which one of the following best describes digitization of sound?
Convert the sound signal into a series of numbers representing the signal’s difference from zero at each moment. - correct
Convert the sound signal into a series of numbers representing the timbre of the signal at each moment.
At each sample moment, record a random number.
At each sample moment, convert the signal into a color: red for low frequencies through violet for high frequencies.
Q2: Why is digital data more resistant to noise?
Because even with noise added, it is relatively easy to distinguish the 0 representation from the 1 representation. - correct
Because anything * 1 is unchanged, the 1’s are error resistant.
Because the digital form includes two copies of the data, there is always a backup copy to use.
Because anything + 0 is unchanged, the 0’s are error resistant.
Week 6 > Digital Media Exercises > Vertical
Q1: Which one of the following is true about the lossy image format JPEG?
It shifts all the colors towards violet so they take up fewer bytes, shifting them back at display time.
It shifts all the colors towards red so they take fewer bytes, shifting them back at display time.
It omits some visual detail so as to take up fewer bytes. - correct
It decreases the width and height of the image so as to take up fewer bytes.
Q2: Which one of the following is a video compression format?
JPEG
PNG
h.264 - correct
Ogg Vorbis
Week 6 > Spreadsheets Exercises > Vertical
Q1: These questions all use the steps.xlsx spreadsheet. Follow the instructions in the spreadsheet to compute sums and averages, then try the questions below.
Look at the computed sums. What is the name of the person with the largest number of steps?
abby
Q2: For the person with the largest number of steps, what is the sum?
80407
Q3: For the person with the largest number of steps, what is their average number of steps (to the nearest whole number)?
893
Week 6 > Computer Security Exercises > Vertical
Q1: Which one of the following is the worst password?
snyrk34
password - correct
XXagflib
XXagflib1
Q2: Which one of the following is the best password?
secret
password1
strawberry
straaabrry - correct
Week 6 > Computer Security 2 Exercises > Vertical
Q1: What is phishing?
The bad guy sends out spam email, forging your address as the from:
The bad guy tricks you into typing your username and password into a fake, bad-guy web site. - correct
The bad guy tricks you into re-shipping packages to Russia.
The bad guy catches a fish, but refuses to share with you.
Q2: What do you check in the browser to check if you are the target of a phishing attack?
Check that the icons and colors of the page look right
Check that the logo and pictures are right
Check that the url up at the top of the browser is right - correct
Check that the date of the page is current
Week 6 > Computer Security 3 Exercises > Vertical
Q1: Which one of the following emails looks like a trojan attack?
This is a very important message from your bank. Please email us your password so we can verify it.
Please visit www.scwhab.bad-guy.ru and log in with your regular password – the standard log-in page is broken today.
I have 27 million dollars here in Spain. If you will send me your contact info to help me transfer the money to your account, I would be happy to give you 10% of it. Please help me, you’re my only hope!
We have detected a virus on your computer. Please download and run this program to check: SuperVirusChecker.exe - correct
Q2: How to best to avoid being attacked through a “vulnerability”?
Reboot your machine each morning.
Avoid web sites where people post pictures of cats.
Keep all your internet-facing software at the latest version. - correct
Always use a fake identity when forum posting.
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