VIDEO solution: 1. Describe at least one rule that could be used by Snort to detect an ACK scan, clearly express assumptions and explain the rule. (2024)

`); let searchUrl = `/search/`; history.forEach((elem) => { prevsearch.find('#prevsearch-options').append(`


`); }); } $('#search-pretype-options').empty(); $('#search-pretype-options').append(prevsearch); let prevbooks = $(false); [ {title:"Recently Opened Textbooks", books:previous_books}, {title:"Recommended Textbooks", books:recommended_books} ].forEach((book_segment) => { if (Array.isArray(book_segment.books) && book_segment.books.length>0 && nsegments<2) { nsegments+=1; prevbooks = $(`

  • ${book_segment.title}
  • `); let searchUrl = "/books/xxx/"; book_segment.books.forEach((elem) => { prevbooks.find('#prevbooks-options'+nsegments.toString()).append(`

    ${elem.title} ${ordinal(elem.edition)} ${}

    `); }); } $('#search-pretype-options').append(prevbooks); }); } function anon_pretype() { let prebooks = null; try { prebooks = JSON.parse(localStorage.getItem('PRETYPE_BOOKS_ANON')); }catch(e) {} if ('previous_books' in prebooks && 'recommended_books' in prebooks) { previous_books = prebooks.previous_books; recommended_books = prebooks.recommended_books; if (typeof PREVBOOKS !== 'undefined' && Array.isArray(PREVBOOKS)) { new_prevbooks = PREVBOOKS; previous_books.forEach(elem => { for (let i = 0; i < new_prevbooks.length; i++) { if ( == new_prevbooks[i].id) { return; } } new_prevbooks.push(elem); }); new_prevbooks = new_prevbooks.slice(0,3); previous_books = new_prevbooks; } if (typeof RECBOOKS !== 'undefined' && Array.isArray(RECBOOKS)) { new_recbooks = RECBOOKS; for (let j = 0; j < new_recbooks.length; j++) { new_recbooks[j].viewed_at = new Date(); } let insert = true; for (let i=0; i < recommended_books.length; i++){ for (let j = 0; j < new_recbooks.length; j++) { if (recommended_books[i].id == new_recbooks[j].id) { insert = false; } } if (insert){ new_recbooks.push(recommended_books[i]); } } new_recbooks.sort((a,b)=>{ adate = new Date(2000, 0, 1); bdate = new Date(2000, 0, 1); if ('viewed_at' in a) {adate = new Date(a.viewed_at);} if ('viewed_at' in b) {bdate = new Date(b.viewed_at);} // 100000000: instead of just erasing the suggestions from previous week, // we just move them to the back of the queue acurweek = ((new Date()).getDate()-adate.getDate()>7)?0:100000000; bcurweek = ((new Date()).getDate()-bdate.getDate()>7)?0:100000000; aviews = 0; bviews = 0; if ('views' in a) {aviews = acurweek+a.views;} if ('views' in b) {bviews = bcurweek+b.views;} return bviews - aviews; }); new_recbooks = new_recbooks.slice(0,3); recommended_books = new_recbooks; } localStorage.setItem('PRETYPE_BOOKS_ANON', JSON.stringify({ previous_books: previous_books, recommended_books: recommended_books })); build_popup(); } } var whiletyping_search_object = null; var whiletyping_search = { books: [], curriculum: [], topics: [] } var single_whiletyping_ajax_promise = null; var whiletyping_database_initial_burst = 0; //number of consecutive calls, after 3 we start the 1 per 5 min calls function get_whiletyping_database() { //gets the database from the server. // 1. by validating against a local database value we confirm that the framework is working and // reduce the ammount of continuous calls produced by errors to 1 per 5 minutes. return localforage.getItem('whiletyping_last_attempt').then(function(value) { if ( value==null || (new Date()) - (new Date(value)) > 1000*60*5 || (whiletyping_database_initial_burst < 3) ) { localforage.setItem('whiletyping_last_attempt', (new Date()).getTime()); // 2. Make an ajax call to the server and get the search database. let databaseUrl = `/search/whiletype_database/`; let resp = single_whiletyping_ajax_promise; if (resp === null) { whiletyping_database_initial_burst = whiletyping_database_initial_burst + 1; single_whiletyping_ajax_promise = resp = new Promise((resolve, reject) => { $.ajax({ url: databaseUrl, type: 'POST', data:{csrfmiddlewaretoken: "vkRG7ofUtCO6P22mNMiMugcNL9GMPB4X2TIhXqkme1vegnXzRZuDbwSt80Eo0LP5"}, success: function (data) { // 3. verify that the elements of the database exist and are arrays if ( ('books' in data) && ('curriculum' in data) && ('topics' in data) && Array.isArray(data.books) && Array.isArray(data.curriculum) && Array.isArray(data.topics)) { localforage.setItem('whiletyping_last_success', (new Date()).getTime()); localforage.setItem('whiletyping_database', data); resolve(data); } }, error: function (error) { console.log(error); resolve(null); }, complete: function (data) { single_whiletyping_ajax_promise = null; } }) }); } return resp; } return Promise.resolve(null); }).catch(function(err) { console.log(err); return Promise.resolve(null); }); } function get_whiletyping_search_object() { // gets the fuse objects that will be in charge of the search if (whiletyping_search_object){ return Promise.resolve(whiletyping_search_object); } database_promise = localforage.getItem('whiletyping_database').then(function(database) { return localforage.getItem('whiletyping_last_success').then(function(last_success) { if (database==null || (new Date()) - (new Date(last_success)) > 1000*60*60*24*30 || (new Date('2023-04-25T00:00:00')) - (new Date(last_success)) > 0) { // New database update return get_whiletyping_database().then(function(new_database) { if (new_database) { database = new_database; } return database; }); } else { return Promise.resolve(database); } }); }); return database_promise.then(function(database) { if (database) { const options = { isCaseSensitive: false, includeScore: true, shouldSort: true, // includeMatches: false, // findAllMatches: false, // minMatchCharLength: 1, // location: 0, threshold: 0.2, // distance: 100, // useExtendedSearch: false, ignoreLocation: true, // ignoreFieldNorm: false, // fieldNormWeight: 1, keys: [ "title" ] }; let curriculum_index={}; let topics_index={}; database.curriculum.forEach(c => curriculum_index[]=c); database.topics.forEach(t => topics_index[]=t); for (j=0; j

  • Textbooks
  • `); } function build_solutions() { if (Array.isArray(solution_search_result)) { const viewAllHTML = userSubscribed ? `View All` : ''; var solutions_section = $(`
  • Solutions ${viewAllHTML}
  • `); let questionUrl = "/questions/xxx/"; let askUrl = "/ask/question/xxx/"; solution_search_result.forEach((elem) => { let url = ('course' in elem)?askUrl:questionUrl; let solution_type = ('course' in elem)?'ask':'question'; let subtitle = ('course' in elem)?(elem.course??""):( ?? "")+"    "+(elem.chapter?"Chapter "+elem.chapter:""); solutions_section.find('#whiletyping-solutions').append(` ${elem.text} ${subtitle} `); }); $('#search-solution-options').empty(); if (Array.isArray(solution_search_result) && solution_search_result.length>0){ $('#search-solution-options').append(solutions_section); } MathJax.typesetPromise([document.getElementById('search-solution-options')]); } } function build_textbooks() { $('#search-pretype-options').empty(); $('#search-pretype-options').append($('#search-solution-options').html()); if (Array.isArray(textbook_search_result)) { var books_section = $(`
  • Textbooks View All
  • `); let searchUrl = "/books/xxx/"; textbook_search_result.forEach((elem) => { books_section.find('#whiletyping-books').append(` ${elem.title} ${ordinal(elem.edition)} ${} `); }); } if (Array.isArray(textbook_search_result) && textbook_search_result.length>0){ $('#search-pretype-options').append(books_section); } } function build_popup(first_time = false) { if ($('#search-text').val()=='') { build_pretype(); } else { solution_and_textbook_search(); } } var search_text_out = true; var search_popup_out = true; const is_login = false; function pretype_setup() { $('#search-text').focusin(function() { $('#search-popup').addClass('show'); resize_popup(); search_text_out = false; }); $( window ).resize(function() { resize_popup(); }); $('#search-text').focusout(() => { search_text_out = true; if (search_text_out && search_popup_out) { $('#search-popup').removeClass('show'); } }); $('#search-popup').mouseenter(() => { search_popup_out = false; }); $('#search-popup').mouseleave(() => { search_popup_out = true; if (search_text_out && search_popup_out) { $('#search-popup').removeClass('show'); } }); $('#search-text').on("keyup", delay(() => { build_popup(); }, 200)); build_popup(true); let prevbookUrl = `/search/pretype_books/`; if (is_login) { $.ajax({ url: prevbookUrl, method: 'POST', data:{csrfmiddlewaretoken: "vkRG7ofUtCO6P22mNMiMugcNL9GMPB4X2TIhXqkme1vegnXzRZuDbwSt80Eo0LP5"}, success: function(response){ previous_books = response.previous_books; recommended_books = response.recommended_books; build_popup(); }, error: function(response){ console.log(response); } }); } else { let prebooks = null; try { prebooks = JSON.parse(localStorage.getItem('PRETYPE_BOOKS_ANON')); }catch(e) {} if (prebooks && 'previous_books' in prebooks && 'recommended_books' in prebooks) { anon_pretype(); } else { $.ajax({ url: prevbookUrl, method: 'POST', data:{csrfmiddlewaretoken: "vkRG7ofUtCO6P22mNMiMugcNL9GMPB4X2TIhXqkme1vegnXzRZuDbwSt80Eo0LP5"}, success: function(response){ previous_books = response.previous_books; recommended_books = response.recommended_books; build_popup(); }, error: function(response){ console.log(response); } }); } } } $( document ).ready(pretype_setup); $( document ).ready(function(){ $('#search-popup').on('click', '.search-view-item', function(e) { e.preventDefault(); let autoCompleteSearchViewUrl = `/search/autocomplete_search_view/`; let objectUrl = $(this).attr('href'); let selectedId = $(this).data('objid'); let searchResults = []; $("#whiletyping-solutions").find("a").each(function() { let is_selected = selectedId === $(this).data('objid'); searchResults.push({ objectId: $(this).data('objid'), contentType: $(this).data('contenttype'), category: $(this).data('category'), selected: is_selected }); }); $("#whiletyping-books").find("a").each(function() { let is_selected = selectedId === $(this).data('objid'); searchResults.push({ objectId: $(this).data('objid'), contentType: $(this).data('contenttype'), category: $(this).data('category'), selected: is_selected }); }); $.ajax({ url: autoCompleteSearchViewUrl, method: 'POST', data:{ csrfmiddlewaretoken: "vkRG7ofUtCO6P22mNMiMugcNL9GMPB4X2TIhXqkme1vegnXzRZuDbwSt80Eo0LP5", query: $('#search-text').val(), searchObjects: JSON.stringify(searchResults) }, dataType: 'json', complete: function(data){ window.location.href = objectUrl; } }); }); });
    VIDEO solution: 1.       Describe
at least one rule that could be used by Snort to detect an ACK
scan, clearly express assumptions and explain the
rule. (2024)


    What is the ACK rule in Snort? ›

    The ack rule option is used to check that the TCP header acknowledgment number is less than, greater than, equal to, not equal to, less than or equal to, or greater than or equal to a specified integer value.

    What are the rules for Snort detection? ›

    The five basic rule types in Snort are: Alert rules: Snort generates an alert when a suspicious packet is detected. Block rules: Snort blocks the suspicious packet and all subsequent packets in the network flow. Drop rules: Snort drops the packet as soon as the alert is generated.

    What is the most common Snort rule? ›

    There are five rule actions by default when executing a standard Snort rule: Alert. Pass, Dynamic, Log, or/and Activate. The most common rule action is “alert,” which, as its name implies, sends an alert to the network administrator if a security threat is detected.

    What is the rule option in Snort? ›

    Rule options are the heart and soul of a Snort rule, as they determine if a given packet should be passed along to its destination, or if it should instead be stopped in its tracks. Each rule option has its own set of option-specific critera, but they all follow the same general structure.

    What are flags in Snort rules? ›

    The flags rule option checks to see if the specified flag bits are set in the TCP header. The following flag bits may be checked: F -> FIN (Finish) S -> SYN (Synchronize sequence numbers)

    What is the use of Snort? ›

    Snort is referred to as a packet sniffer that monitors network traffic, scrutinizing each packet closely to detect a dangerous payload or suspicious anomalies. Long a leader among enterprise intrusion prevention and detection tools, users can compile Snort on most Linux operating systems (OSes) or Unix.

    Does Snort have anomaly detection? ›

    The first two types of preprocessors enhance Snort's rule checking and add substantial protocol anomaly detection. They allow Snort to perform rule checking across packets and within nontrivial protocols.

    What is the exclamation mark in Snort rule? ›

    Snort provides a mechanism to exclude addresses by the use of the negation symbol !, an exclamation point. This symbol is used with the address to direct Snort not to test packets coming from or going to that address.

    How to write local rules in Snort? ›

    1. Click the SNORT Rules tab.
    2. Do one or both of the following tasks: In the Import SNORT Rule File area, click Select *. rules file(s) to import, navigate to the applicable rules file on the system, and open it. In the Rules area, click the Add icon to add unique SNORT rules and to set the following options:

    What is the flow rule in Snort? ›

    Flow: In Snort Rules, flow refers to the direction of the traffic. This keyword/symbol helps us apply rules only to the specific parts of the traffic.

    What is the threshold rule in Snort? ›

    This rule logs every 10th event on this SID during a 60 second interval. So if less than 10 events occur in 60 seconds, nothing gets logged. Once an event is logged, a new time period starts for type=threshold. This rule logs at most one event every 60 seconds if at least 10 events on this SID are fired.

    What are the keywords for Snort rules? ›

    The sid keyword is used to uniquely identify Snort rules. The rev keyword is used to uniquely identify revisions of Snort rules. The classtype keyword is used to categorize a rule as detecting an attack that is part of a more general type of attack class. The priority keyword assigns a severity level to rules.

    What is a Snort detection rule? ›

    Rules are a different methodology for performing detection, which bring the advantage of 0-day detection to the table. Unlike signatures, rules are based on detecting the actual vulnerability, not an exploit or a unique piece of data.

    Where to find Snort rules? ›

    You can download the rules and deploy them in your network through the website. The Community Ruleset is developed by the Snort community and QAed by Cisco Talos. It is freely available to all users.

    What is the SID rule in Snort? ›

    The sid keyword uniquely identifies a given Snort rule. This rule option takes in a single argument that is a numeric value that must be unique to the rule. While not technically required, all Snort rules should have a sid option to be able to quickly identify a rule should it ever generate an alert.

    What are the three modes of Snort? ›

    Sniffer mode, which simply reads the packets off of the network and displays them for you in a continuous stream on the console (screen). Packet Logger mode, which logs the packets to disk. Network Intrusion Detection System (NIDS) mode, which performs detection and analysis on network traffic.

    What are the two sections of a Snort rule? ›

    Snort rules are divided into two logical sections, the rule header and the rule options. The rule header contains the rule's action, protocol, source and destination IP addresses and netmasks, and the source and destination ports information.

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