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<?php |
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/** |
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* @copyright Copyright (c) 2018 Matthias Held <[email protected]> |
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* @author Matthias Held <[email protected]> |
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* @license GNU AGPL version 3 or any later version |
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* |
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* This program is free software: you can redistribute it and/or modify |
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* it under the terms of the GNU Affero General Public License as |
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* published by the Free Software Foundation, either version 3 of the |
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* License, or (at your option) any later version. |
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* |
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* This program is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU Affero General Public License for more details. |
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* |
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* You should have received a copy of the GNU Affero General Public License |
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* along with this program. If not, see <https://www.gnu.org/licenses/>. |
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*/ |
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namespace OCA\RansomwareDetection\Analyzer; |
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use OCA\RansomwareDetection\Monitor; |
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use OCA\RansomwareDetection\Classifier; |
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class SequenceAnalyzer |
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{ |
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/** |
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* Number of information files. |
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* |
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* @var int |
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*/ |
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const NUMBER_OF_INFO_FILES = 10; |
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/** @var SequenceSizeAnalyzer */ |
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private $sequenceSizeAnalyzer; |
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/** @var FileTypeFunnellingAnalyzer */ |
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private $fileTypeFunnellingAnalyzer; |
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/** @var EntropyFunnellingAnalyzer */ |
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private $entropyFunnellingAnalyzer; |
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/** |
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* SequenceAnalyzer constructor. |
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* |
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* @param SequenceSizeAnalyzer $sequenceSizeAnalyzer |
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* @param FileTypeFunnellingAnalyzer $fileTypeFunnellingAnalyzer |
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* @param EntropyFunnellingAnalyzer $entropyFunnellingAnalyzer |
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*/ |
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public function __construct( |
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SequenceSizeAnalyzer $sequenceSizeAnalyzer, |
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FileTypeFunnellingAnalyzer $fileTypeFunnellingAnalyzer, |
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EntropyFunnellingAnalyzer $entropyFunnellingAnalyzer |
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) { |
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$this->sequenceSizeAnalyzer = $sequenceSizeAnalyzer; |
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$this->fileTypeFunnellingAnalyzer = $fileTypeFunnellingAnalyzer; |
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$this->entropyFunnellingAnalyzer = $entropyFunnellingAnalyzer; |
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} |
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/** |
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* The analysis of the sequence is seperated in three parts: |
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* The analysis: If the same number of files is deletedFilesd as written, |
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* with the special addition that the number of written files is in the |
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* range of [number of deletedFilesd files, number of deletedFilesd files + 4]. |
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* To enhance this analysis the sum of the size of the files deletedFilesd and |
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* the sum of the size of the written files is compared. |
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* |
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* The next part is the analysis of the suspicion levels of the files written. |
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* Therefor the suspicions levels are weighted: |
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* Suspicious - 1 |
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* Maybe suspicious - 0.5 |
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* Not suspicious - 0 |
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* |
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* summed up and divided by the sum of all written files. The higher the result, |
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* the higher is the suspicion of the hole sequence. |
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* |
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* The last part is the file type funneling analysis. |
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* |
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* @param int $sequenceId |
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* @param array $sequence |
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* |
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* @return SequenceResult |
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*/ |
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public function analyze($sequenceId, $sequence) |
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{ |
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$sequenceResult = new SequenceResult($sequenceId, 0, 0, 0, 0, $sequence); |
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if (sizeof($sequence) === 0) { |
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return $sequenceResult; |
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} |
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$files = ['written' => [], 'sizeWritten' => 0, 'deleted' => [], 'sizeDeleted' => 0, 'suspicious' => [], 'maybeSuspicious' => [], 'notSuspicious' => []]; |
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$suspicionScore = 0; |
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foreach ($sequence as $file) { |
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if ($file->getType() === 'file') { |
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switch ($file->getCommand()) { |
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case Monitor::WRITE: |
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$files['written'][] = $file; |
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$files['sizeWritten'] = $files['sizeWritten'] + $file->getSize(); |
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break; |
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case Monitor::READ: |
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break; |
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case Monitor::RENAME: |
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break; |
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case Monitor::DELETE: |
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$files['deleted'][] = $file; |
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$files['sizeDeleted'] = $files['sizeDeleted'] + $file->getSize(); |
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break; |
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case Monitor::CREATE: |
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break; |
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default: |
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break; |
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} |
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switch ($file->getSuspicionClass()) { |
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case Classifier::SUSPICIOUS: |
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$files['suspicious'][] = $file; |
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break; |
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case Classifier::MAYBE_SUSPICIOUS: |
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$files['maybeSuspicious'][] = $file; |
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break; |
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case Classifier::NOT_SUSPICIOUS: |
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$files['notSuspicious'][] = $file; |
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break; |
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case Classifier::NO_INFORMATION: |
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break; |
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default: |
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break; |
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} |
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} |
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} |
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// compare files written and files deleted |
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if (sizeof($files['written']) > 0 && sizeof($files['deleted']) > 0) { |
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$sequenceResult->setSizeWritten($files['sizeWritten']); |
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$sequenceResult->setSizeDeleted($files['sizeDeleted']); |
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$upperBound = sizeof($files['deleted']) + self::NUMBER_OF_INFO_FILES; |
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if (sizeof($files['written']) <= $upperBound && sizeof($files['written']) >= sizeof($files['deleted'])) { |
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if ($this->sequenceSizeAnalyzer->analyze($sequence) === SequenceSizeAnalyzer::EQUAL_SIZE) { |
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$sequenceResult->setQuantities(2); |
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$suspicionScore += 1; |
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} else { |
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$sequenceResult->setQuantities(1); |
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$suspicionScore += 0; |
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} |
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} |
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} |
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$numberOfWrittenFiles = sizeof($files['suspicious']) + sizeof($files['maybeSuspicious']) + sizeof($files['notSuspicious']); |
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// remove info files from the weight |
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$numberOfInfoFiles = self::NUMBER_OF_INFO_FILES; |
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if (sizeof($files['notSuspicious']) < self::NUMBER_OF_INFO_FILES) { |
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$numberOfInfoFiles = sizeof($files['notSuspicious']); |
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} |
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// weight the suspicion levels. |
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$suspicionSum = (sizeof($files['suspicious']) * 1) + (sizeof($files['maybeSuspicious']) * 0.5); |
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// check for division by zero. |
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if (($numberOfWrittenFiles - $numberOfInfoFiles) > 0) { |
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$sequenceResult->setFileSuspicion($suspicionSum / ($numberOfWrittenFiles - $numberOfInfoFiles)); |
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$suspicionScore += $suspicionSum / ($numberOfWrittenFiles - $numberOfInfoFiles); |
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} |
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// entropy funnelling |
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$entropyFunnelling = $this->entropyFunnellingAnalyzer->analyze($files['deleted'], $files['written']); |
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$sequenceResult->setEntropyFunnelling($entropyFunnelling); |
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$suspicionScore += $entropyFunnelling->getEntropyFunnelling(); |
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// check for file type funneling |
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$fileTypeFunnelling = $this->fileTypeFunnellingAnalyzer->analyze($sequence); |
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$sequenceResult->setFileTypeFunnelling($fileTypeFunnelling); |
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$suspicionScore += $fileTypeFunnelling; |
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$sequenceResult->setSuspicionScore($suspicionScore); |
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return $sequenceResult; |
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} |
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} |
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undo-ransomware /
ransomware_detection
