CS代写 Computer Science 571 2nd Exam Prof. , December 3, 2015, 6:00pm – 7:20pm

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lines is 2 points each.
Web Security Questions [10 pts]

Each question is worth 2 points.
Q1: What are common ways that websites get infected?
[X] SQL Injection attacks
[ ] XSP Scripting attacks
[X ] Search Engine result redirection
[X] Using social networking sites to infect users [X] Attacks on back end virtual hosting companies [ ] ALL OF THE ABOVE
Q2: Give one example of “weak” password recovery validation A2:
Any one of these:
1) Information Verification: Asking the user to supply their email address along with their phone number. Note that these are both publicly available.
2) Password Hints: Many users have a tendency to embed the password in the hint itself.
3) Secret Question + Answer: Something like “In which city were you born?” for a password recovery system is easily circumventable today because most of the information is public due to social networking sites.
Q3: What is a JSON array vulnerable to?
A3: JavaScript Hijacking
Q4: Name two techniques used to bypass the same-origin policy. A4:
Any one of these:
1) JSON and the Dynamic Script Tag
3) AJAX Proxy
4) Browser Extensions and plugins
Q5: What used to be the problem of Domain Keys Identified Mail (DKIM) as implemented by Google Mail?

A5: DKIM keys were too short and could be factored in 24 hours using a notebook.
HTML5 Questions [10 pts]
Each question is worth 2 points.
Q1: In a element what is the purpose of the “id” attribute? A1: to obtain the “drawing context” using getContext()
Q2: Which of the following are new elements in HTML5?
[X] article [X] aside
[ ] applet [X] header [ ] column [X] nav
[ ] ALL OF THE ABOVE
Q3: Which of the following are removed elements in HTML5?
[X] center
[ ] footer
[X] applet
[X] frameset
[ ] ALL OF THE ABOVE
Q4: Name three new elements requested by newspaper publishers? A4: Any 3 of header, footer, nav, article, section, aside.
Q5: What is the required attribute of the

Q1: What Rule is this code an example of?
uF(this.L,this.Q,new G(b[a].x,b[a].y));var
c,d,e,f=$L(this,a),g=aM(this,a);e=b=c=d=0;
A1: Minification or Obfuscation of JavaScript
Q2: Why are CSS Expressions to be avoided?
A2: Because they may execute many times, on mouse clicks, keyboard presses, etc.
Q3: Why using a large number of hostnames in a web page is not good for performance?
A3: Because each hostname may involve a time consuming DNS lookup
Q4: When is the use of ETags not recommended?
A4: When using “farms” of UNIX servers.
Q5: What is the interaction between favicon.ico and cookies and how do you optimize it?
A5: Each time the browser request this file, the root cookies are sent, so they should be small
JSON Questions [10 pts]
All questions are worth 2 points.
Q1: What is the MIME type for JSON?
A1: application/json
Q2: Consider the following script:

What is the output that gets produced?

Q3: What is a JSON “object”?
A3: A collection of key:value pairs, comma-separated and enclosed in curly brackets Q4: When should you use arrays when modeling your data in JSON?
A4: When key names are sequential integers.
Q5: What is the following code?
// Constructor -- pass a REST request URL to the constructor
function JSONscriptRequest(fullUrl) {
// REST request path
this.fullUrl = fullUrl;
// Keep IE from caching requests
this.noCacheIE = '&noCacheIE=' + (new Date()).getTime();
// Get the DOM location to put the script tag
this.headLoc = document.getElementsByTagName("head").item(0); // Generate a unique script tag id
this.scriptId = 'JscriptId' + JSONscriptRequest.scriptCounter++; }
// Static script ID counter
JSONscriptRequest.scriptCounter = 1;
// buildScriptTag method JSONscriptRequest.prototype.buildScriptTag = function () { // Create the script tag
this.scriptObj = document.createElement("script");
// Add script object attributes this.scriptObj.setAttribute("type", "text/javascript"); this.scriptObj.setAttribute("charset", "utf-8"); this.scriptObj.setAttribute("src", this.fullUrl + this.noCacheIE);
this.scriptObj.setAttribute("id", this.scriptId); }
// removeScriptTag method JSONscriptRequest.prototype.removeScriptTag = function () { // Destroy the script tag this.headLoc.removeChild(this.scriptObj); }
// addScriptTag method JSONscriptRequest.prototype.addScriptTag = function () {
// Create the script tag

this.headLoc.appendChild(this.scriptObj); }
A5: Source code from the Dynamic Script Tag “Hack.” AJAX Questions [10 pts]
All questions are worth 2 points
Q1: Of the URLs below, which have the same origin?
a. http://www.ajaxbook.com
b. http://www.ajaxbook.com:8443 c. https://www.ajaxbook.com
d. http://ajaxbook.com
e. http://www.ajaxbook.com:80
A1: a and e –OR- “none” (depending on the browser)
Q2: Which of the following are common characteristics of AJAX applications?
[X] They allow for smooth, continuous interaction [X] May provide "Live" content
[X] May have visual effects
[X] May include animations and dynamic icons
[ ] May include Google Map widgets
[X] May include custom selectors and buttons [X] May use drag-and-drop
[X] May implement double-click
[ ] ALL OF THE ABOVE
Q3: What is returned by the getAllResponseHeaders() method of the XMLHttpRequest() object?
A3: A “string” containing a complete set of HTTP response headers Q4: What are two very common values of the “status” property of the
XMLHttpRequest() object? A4: 400, 404 and 200
Q5: What is a common way to work around the cross-domain restriction of XMLHttpRequest()?
A5: Use a proxy –OR- CORS

Cookies and Privacy Questions [10 pts]
Q1: Complete the PHP code to set a cookie with name “username2” and value “Barney rubble”, and expiring in an hour:
setcookie("username2", "Barney rubble", time()+3600);
Click here to view the cookie

Q2: Complete the PHP code to view the value of a cookie named “username2”. Ensure that the cookie exists.
if( isset($_COOKIE["username2"]) ) {
echo "The new cookie username2 contains the value " .
$_COOKIE["username2"];
JQuery Questions [10 pts]
Q1: (2 points) What is the JQuery code that corresponds to the following?
var myButton = document.getElementById("myButton");
A1: $("#myButton");
Q2: (2 points) What are three examples of JQuery “basic” selectors?
A2: Any 3 of All, Class, Element, ID and Multiple.
Q3: [This question is worth 6 points] Consider the following example without JQuery:
hex=255; // Initial color value. function fadetext() {
if(hex>0) { //If color is not black yet hex -= 11; // increase color darkness
document.getElementById("sample").style.color="rgb("+hex+","+hex+","+hex+")" ;
setTimeout("fadetext()",20); } else hex=255; //reset hex value
A3: Rewrite it using JQuery. Assume fadeText is the id of the button.
$(function() { // when document is ready
$("#fadeText").click(function() { // set a onClick handler on fadeText
$("#sample").fadeOut(125).delay().fadeIn(125);
// fadeOut the sample for 125 ms, delay, then fadeIn for 125 ms

Lynda.com & Guest Questions [10 pts]
Each question is worth 1 point.
Q1: Cookies can be stolen in two major ways. Mention two of them.
A1: (1) using XSS attach and (2) sniffing network traffic
Q2: How can you avoid having cookies stolen using document.cookie? Mention one avoidance methodology.
A2: (1) Use HttpOnly cookies (i.e., use server-based cookies), (b) use Secure cookies (HTTPS only)
Q3: Why session hijacking is worse than cookie theft?
A3: Because sessionsID usually contain your logged in status and can be used to assume
your identity.
Q4: In what kind of design would you use the following meta tag?
A4: In “responsive” design
Q5: What is screen density?
A5: the number of (hardware) pixels within a physical area of the screen, like 256ppi (pixels per inch)
Q6: What is a reference pixel?
A6: Also know as “CSS pixel”, it is a unit a measurement that establishes an optical standard for the length of a pixel, independent of hardware pixels. Referenced in the W3C standard for CSS.
Q7: How can you make issues with scaling factors of images go away? Name one such methodology.
A7: (a) Use SVG (resolution-independent vector graphics) or (2) CSS Q8: When would you use the “uncompressed” version go jQuery? A8: During development

Q9: If you were using jQuery for 1 (one) single thing, what would you use and why? A9: jQuery AJAX functions, because allows AJAX code to be browser independent. Q10: What is the major difference between “waterfall” and “scrum” development? A10: sequential (waterfall) vs iterative (scrum / agile)

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