Browser Isolation: The Future of Secure Web Browsing in 2026

Complete Browser Isolation Policy Manager:

/**
 * Production-ready Browser Isolation Policy Manager
 * Comprehensive policy engine for browser isolation
 */

class BrowserIsolationPolicyManager {
    constructor(config = {}) {
        this.config = {
            isolationServiceUrl: config.isolationServiceUrl || 'https://isolation.example.com',
            apiKey: config.apiKey,
            ...config
        };
        
        this.policies = {
  alwaysIsolate: [
                /\.onion$/i,           // Tor sites
                /\.bit$/i,             // Namecoin
                /malware/i,
                /phishing/i,
                /test-malware/i
            ],
  riskBasedIsolation: {
                enabled: true,
                threshold: 0.7,
                factors: {
                    domainAge: 0.2,        // New domains = higher risk
                    reputation: 0.3,       // Low reputation = higher risk
                    content: 0.2,          // Suspicious content = higher risk
                    certificate: 0.15,     // Invalid cert = higher risk
                    blacklist: 0.15        // Blacklist matches = higher risk
                }
            },
  isolateUnknown: true,
            isolateDownloads: true,
            trustedDomains: new Set([
                'google.com',
                'microsoft.com',
                'github.com'
            ])
        };
        
        this.domainCache = new Map();
        this.isolationSession = null;
    }
    
    /**
     * Check if URL should be isolated
     * @param {string} url - URL to check
     * @returns {Promise<{shouldIsolate: boolean, reason: string, riskScore: number}>}
     */
    async shouldIsolate(url) {
        try {
            const urlObj = new URL(url);
            const domain = urlObj.hostname;
            
            // Check always-isolate patterns
            for (const pattern of this.policies.alwaysIsolate) {
                if (pattern.test(domain)) {
                    return {
                        shouldIsolate: true,
                        reason: 'Matches always-isolate pattern',
                        riskScore: 1.0
                    };
                }
            }
            
            // Check trusted domains
            if (this.policies.trustedDomains.has(domain)) {
                return {
                    shouldIsolate: false,
                    reason: 'Trusted domain',
                    riskScore: 0.0
                };
            }
            
            // Check if unknown domain
            if (this.policies.isolateUnknown && !await this.isKnownDomain(domain)) {
                return {
                    shouldIsolate: true,
                    reason: 'Unknown domain',
                    riskScore: 0.6
                };
            }
            
            // Calculate risk score
            if (this.policies.riskBasedIsolation.enabled) {
                const riskScore = await this.calculateRiskScore(url, domain);
                
                if (riskScore > this.policies.riskBasedIsolation.threshold) {
                    return {
                        shouldIsolate: true,
                        reason: 'High risk score',
                        riskScore: riskScore
                    };
                }
            }
            
            return {
                shouldIsolate: false,
                reason: 'Low risk',
                riskScore: 0.0
            };
        } catch (error) {
            console.error('Error checking isolation policy:', error);
            // Default to isolation on error (fail-secure)
            return {
                shouldIsolate: true,
                reason: 'Error in policy check',
                riskScore: 0.8
            };
        }
    }
    
    /**
     * Calculate risk score for URL
     * @param {string} url - URL to analyze
     * @param {string} domain - Domain name
     * @returns {Promise<number>} Risk score 0.0-1.0
     */
    async calculateRiskScore(url, domain) {
        const factors = this.policies.riskBasedIsolation.factors;
        let score = 0;
        
        // Domain age (newer = riskier)
        const domainAge = await this.getDomainAge(domain);
        if (domainAge < 90) { // Less than 90 days
            score += factors.domainAge * (1 - domainAge / 90);
        }
        
        // Reputation check
        const reputation = await this.checkDomainReputation(domain);
        if (reputation < 0.5) {
            score += factors.reputation * (1 - reputation);
        }
        
        // Certificate check
        const certValid = await this.checkCertificate(url);
        if (!certValid) {
            score += factors.certificate;
        }
        
        // Blacklist check
        const isBlacklisted = await this.checkBlacklist(domain);
        if (isBlacklisted) {
            score += factors.blacklist;
        }
        
        // Content analysis (if accessible)
        try {
            const contentRisk = await this.analyzeContentRisk(url);
            score += factors.content * contentRisk;
        } catch (e) {
            // Content not accessible, skip
        }
        
        return Math.min(1.0, Math.max(0.0, score));
    }
    
    /**
     * Get domain age in days
     */
    async getDomainAge(domain) {
        // Cache domain age
        if (this.domainCache.has(domain)) {
            return this.domainCache.get(domain).age;
        }
        
        try {
            // Query WHOIS or use API
            const response = await fetch(`https://api.whoisjson.com/v1/${domain}`);
            const data = await response.json();
            
            if (data.created_date) {
                const created = new Date(data.created_date);
                const age = (Date.now() - created.getTime()) / (1000 * 60 * 60 * 24);
                this.domainCache.set(domain, { age, timestamp: Date.now() });
                return age;
            }
        } catch (e) {
            // Fallback: assume unknown age = medium risk
            return 180;
        }
        
        return 180; // Default: assume 6 months old
    }
    
    /**
     * Check domain reputation
     */
    async checkDomainReputation(domain) {
        try {
            // Use reputation API (e.g., VirusTotal, AbuseIPDB)
            const response = await fetch(`https://api.reputation.example.com/check/${domain}`, {
                headers: {
                    'Authorization': `Bearer ${this.config.apiKey}`
                }
            });
            const data = await response.json();
            return data.reputation || 0.5; // Default to neutral
        } catch (e) {
            return 0.5; // Default to neutral on error
        }
    }
    
    /**
     * Check certificate validity
     */
    async checkCertificate(url) {
        try {
            const response = await fetch(url, { method: 'HEAD', mode: 'no-cors' });
            // In real implementation, check certificate chain
            return true; // Simplified
        } catch (e) {
            return false;
        }
    }
    
    /**
     * Check domain blacklist
     */
    async checkBlacklist(domain) {
        const blacklists = [
            'malware-domains.txt',
            'phishing-domains.txt'
        ];
        
        // Check against blacklists (simplified)
        // In production, use actual blacklist APIs
        return false;
    }
    
    /**
     * Analyze content risk
     */
    async analyzeContentRisk(url) {
        try {
            // Fetch and analyze content
            const response = await fetch(url, {
                headers: {
                    'User-Agent': 'Mozilla/5.0'
                }
            });
            const html = await response.text();
            
            // Check for suspicious patterns
            const suspiciousPatterns = [
                /malware/i,
                /phishing/i,
                /exploit/i,
                /<script[^>]*eval/i,
                /base64.*decode/i
            ];
            
            let risk = 0;
            for (const pattern of suspiciousPatterns) {
                if (pattern.test(html)) {
                    risk += 0.2;
                }
            }
            
            return Math.min(1.0, risk);
        } catch (e) {
            return 0.0;
        }
    }
    
    /**
     * Check if domain is known/trusted
     */
    async isKnownDomain(domain) {
        // Check against trusted domain list
        if (this.policies.trustedDomains.has(domain)) {
    return true;
  }
  
        // Check domain age (older = more likely known)
        const age = await this.getDomainAge(domain);
        return age > 365; // Older than 1 year = likely known
    }
    
    /**
     * Create isolated browser session
     */
    async createIsolationSession(url) {
        try {
            const response = await fetch(`${this.config.isolationServiceUrl}/api/sessions`, {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/json',
                    'Authorization': `Bearer ${this.config.apiKey}`
                },
                body: JSON.stringify({
                    url: url,
                    options: {
                        sandbox: true,
                        networkIsolation: true,
                        fileDownloadIsolation: this.policies.isolateDownloads
                    }
                })
            });
            
            const session = await response.json();
            this.isolationSession = session;
            return session;
        } catch (error) {
            console.error('Error creating isolation session:', error);
            throw error;
        }
    }
    
    /**
     * Redirect to isolated browser session
     */
    async redirectToIsolation(url) {
        const decision = await this.shouldIsolate(url);
        
        if (decision.shouldIsolate) {
            const session = await this.createIsolationSession(url);
            window.location.href = session.viewerUrl;
    return true;
  }
  
  return false;
}
}

// Browser extension integration
class BrowserIsolationExtension {
    constructor() {
        this.policyManager = new BrowserIsolationPolicyManager({
            isolationServiceUrl: 'https://isolation.example.com',
            apiKey: 'your-api-key'
        });
        
        this.init();
    }
    
    init() {
        // Intercept link clicks
        document.addEventListener('click', async (e) => {
            const link = e.target.closest('a');
            if (link && link.href) {
                const shouldIsolate = await this.policyManager.shouldIsolate(link.href);
                if (shouldIsolate.shouldIsolate) {
                    e.preventDefault();
                    await this.policyManager.redirectToIsolation(link.href);
                }
            }
        }, true);
        
        // Intercept navigation
        window.addEventListener('beforeunload', async (e) => {
            const url = window.location.href;
            const shouldIsolate = await this.policyManager.shouldIsolate(url);
            if (shouldIsolate.shouldIsolate && !this.isolationSession) {
                e.preventDefault();
                await this.policyManager.redirectToIsolation(url);
            }
        });
    }
}

// Server-side isolation proxy (Node.js/Express)
const express = require('express');
const { createProxyMiddleware } = require('http-proxy-middleware');

const app = express();

app.use(async (req, res, next) => {
    const url = req.protocol + '://' + req.get('host') + req.originalUrl;
    const policyManager = new BrowserIsolationPolicyManager();
    
    const decision = await policyManager.shouldIsolate(url);
    
    if (decision.shouldIsolate) {
        // Proxy to isolation service
        const isolationUrl = `https://isolation.example.com/proxy?url=${encodeURIComponent(url)}`;
        res.redirect(isolationUrl);
    } else {
        next();
    }
});

app.listen(3000, () => {
    console.log('Isolation proxy server running on port 3000');
});

# Docker Compose example for isolated browser
version: '3.8'
services:
  isolated-browser:
    image: browserless/chrome:latest
    network_mode: isolated
    environment:
      - CONNECTION_TIMEOUT=60000
      - MAX_CONCURRENT_SESSIONS=10
    volumes:
      - ./sandbox:/sandbox
    # No host network access
    # All traffic stays in isolated network
    
  proxy:
    image: nginx:alpine
    ports:
      - "8080:80"
    volumes:
      - ./nginx.conf:/etc/nginx/nginx.conf
    depends_on:
      - isolated-browser

// Email link isolation with real implementations
class EmailLinkIsolation {
  constructor() {
    // Trusted domains list (should be maintained/updated regularly)
    this.trustedDomains = new Set([
      'example.com',
      'trusted-partner.com',
      // Add your trusted domains here
    ]);
    
    // Known malicious domains (can be loaded from threat intelligence)
    this.maliciousDomains = new Set([
      // Load from threat intelligence feed
    ]);
    
    // Sender reputation cache
    this.senderReputationCache = new Map();
  }
  
  // Check sender reputation based on domain and history
  getSenderReputation(sender) {
    // Check cache first
    if (this.senderReputationCache.has(sender)) {
      return this.senderReputationCache.get(sender);
    }
    
    try {
      const senderDomain = sender.split('@')[1]?.toLowerCase();
      if (!senderDomain) return 0.0;
      
      // Check if sender domain is trusted
      if (this.trustedDomains.has(senderDomain)) {
        this.senderReputationCache.set(sender, 1.0);
        return 1.0;
      }
      
      // Check if sender domain is malicious
      if (this.maliciousDomains.has(senderDomain)) {
        this.senderReputationCache.set(sender, 0.0);
        return 0.0;
      }
      
      // Check domain age and SPF/DKIM (simplified - in production, use proper email security APIs)
      const domainAge = this.getDomainAge(senderDomain);
      const hasSPF = this.checkSPF(senderDomain);
      const hasDKIM = this.checkDKIM(senderDomain);
      
      // Calculate reputation score
      let score = 0.5; // Default neutral
      if (domainAge > 365) score += 0.2; // Older domains are more trusted
      if (hasSPF) score += 0.15;
      if (hasDKIM) score += 0.15;
      
      score = Math.min(1.0, Math.max(0.0, score));
      this.senderReputationCache.set(sender, score);
      return score;
    } catch (error) {
      console.error('Error calculating sender reputation:', error);
      return 0.0; // Fail closed
    }
  }
  
  // Check URL reputation
  getURLReputation(url) {
    try {
      const urlObj = new URL(url);
      const domain = urlObj.hostname.toLowerCase();
      
      // Check if domain is trusted
      if (this.trustedDomains.has(domain)) {
        return 1.0;
      }
      
      // Check if domain is malicious
      if (this.maliciousDomains.has(domain)) {
        return 0.0;
      }
      
      // Check for suspicious patterns
      if (this.isSuspiciousDomain(domain)) {
        return 0.3;
      }
      
      // Default to neutral
      return 0.5;
    } catch (error) {
      console.error('Error calculating URL reputation:', error);
      return 0.0;
    }
  }
  
  // Check if domain is known/trusted
  isKnownDomain(domain) {
    const normalizedDomain = domain.toLowerCase();
    return this.trustedDomains.has(normalizedDomain);
  }
  
  // Helper: Get domain age (simplified - in production, use WHOIS API)
  getDomainAge(domain) {
    // In production, use WHOIS API or domain age service
    // For now, return a default value
    return 730; // Assume 2 years old
  }
  
  // Helper: Check SPF record (simplified)
  checkSPF(domain) {
    // In production, perform DNS TXT lookup for SPF record
    // For now, return true for known good domains
    return this.trustedDomains.has(domain);
  }
  
  // Helper: Check DKIM (simplified)
  checkDKIM(domain) {
    // In production, check for DKIM DNS records
    // For now, return true for known good domains
    return this.trustedDomains.has(domain);
  }
  
  // Helper: Check for suspicious domain patterns
  isSuspiciousDomain(domain) {
    // Check for typosquatting patterns
    const suspiciousPatterns = [
      /[0-9]{4,}/,  // Many numbers
      /-[a-z]{1,2}-/,  // Suspicious subdomain patterns
      /bit\.ly|tinyurl|t\.co/,  // URL shorteners (often used in phishing)
    ];
    
    return suspiciousPatterns.some(pattern => pattern.test(domain));
  }
  
  // Process email link and decide on isolation
  processEmailLink(url, sender) {
    try {
      // Check sender reputation
      const senderReputation = this.getSenderReputation(sender);
      
      // Check URL reputation
      const urlReputation = this.getURLReputation(url);
      
      // Isolate if sender or URL is untrusted
      if (senderReputation < 0.5 || urlReputation < 0.5) {
        return {
          action: 'isolate',
          reason: 'Untrusted source or URL',
          senderReputation,
          urlReputation
        };
      }
      
      // Isolate if domain is unknown
      const domain = new URL(url).hostname.toLowerCase();
      if (!this.isKnownDomain(domain)) {
        return {
          action: 'isolate',
          reason: 'Unknown domain',
          domain
        };
      }
      
      return {
        action: 'allow',
        reason: 'Trusted source and URL',
        senderReputation,
        urlReputation
      };
    } catch (error) {
      console.error('Error processing email link:', error);
      // Fail closed - isolate on error
      return {
        action: 'isolate',
        reason: 'Error processing link',
        error: error.message
      };
    }
  }
  
  // Open URL in isolated browser (production implementation)
  openInIsolatedBrowser(url) {
    // In production, integrate with browser isolation service
    // Example: Cloudflare Browser Isolation, Menlo Security, etc.
    const isolationUrl = `https://isolated-browser.example.com/proxy?url=${encodeURIComponent(url)}`;
    window.open(isolationUrl, '_blank', 'noopener,noreferrer');
    
    // Log isolation event
    this.logIsolationEvent({
      type: 'isolate',
      url,
      reason: 'Email link isolation',
      timestamp: new Date().toISOString()
    });
  }
  
  // Log isolation events
  logIsolationEvent(event) {
    // In production, send to logging service
    console.log('Browser isolation event:', event);
    // Example: sendToLoggingService(event);
  }
}

// Usage
const emailIsolation = new EmailLinkIsolation();

// Apply to email client
function handleEmailLinkClick(url, email) {
  const decision = emailIsolation.processEmailLink(url, email.sender);
  
  if (decision.action === 'isolate') {
    emailIsolation.openInIsolatedBrowser(url);
  } else {
    window.open(url, '_blank', 'noopener,noreferrer');
  }
}

// Example integration
document.addEventListener('click', (e) => {
  const link = e.target.closest('a[href^="http"]');
  if (link && link.dataset.emailSender) {
    e.preventDefault();
    handleEmailLinkClick(link.href, { sender: link.dataset.emailSender });
  }
});

// Download isolation with real implementations
class DownloadIsolation {
  constructor() {
    this.downloadPolicy = {
      // Always isolate these file types
      alwaysIsolate: ['.exe', '.dll', '.bat', '.ps1', '.scr', '.vbs', '.msi', '.jar'],
      
      // Isolate based on source
      isolateFromUntrusted: true,
      
      // Scan before allowing download
      scanBeforeDownload: true
    };
    
    // Trusted download sources
    this.trustedSources = new Set([
      'https://download.microsoft.com',
      'https://downloads.example.com',
      // Add your trusted sources
    ]);
  }
  
  // Check if source is trusted
  isTrustedSource(url) {
    try {
      const urlObj = new URL(url);
      const origin = urlObj.origin.toLowerCase();
      
      // Check exact match
      if (this.trustedSources.has(origin)) {
        return true;
      }
      
      // Check if from same origin (current site)
      if (origin === window.location.origin.toLowerCase()) {
        return true;
      }
      
      return false;
    } catch (error) {
      console.error('Error checking source:', error);
      return false; // Fail closed
    }
  }
  
  // Scan file using antivirus/EDR API (production implementation)
  async scanFile(url) {
    try {
      // In production, integrate with antivirus/EDR service
      // Example: VirusTotal API, CrowdStrike, etc.
      const response = await fetch('/api/scan-file', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ url })
      });
      
      const result = await response.json();
      return {
        malicious: result.malicious || false,
        threatName: result.threatName || null,
        scanDate: result.scanDate || new Date().toISOString()
      };
    } catch (error) {
      console.error('Error scanning file:', error);
      // Fail closed - treat as potentially malicious
      return { malicious: true, error: error.message };
    }
  }
  
  // Download to isolated environment
  downloadToIsolatedEnvironment(url, filename) {
    // In production, integrate with browser isolation service
    const isolationUrl = `https://isolated-browser.example.com/download?url=${encodeURIComponent(url)}&filename=${encodeURIComponent(filename)}`;
    
    // Open in isolated browser for download
    window.open(isolationUrl, '_blank', 'noopener,noreferrer');
    
    // Log isolation event
    this.logDownloadEvent({
      type: 'isolated',
      url,
      filename,
      reason: 'File type or source isolation policy',
      timestamp: new Date().toISOString()
    });
  }
  
  // Normal download
  downloadNormally(url, filename) {
    // Create temporary link and trigger download
    const link = document.createElement('a');
    link.href = url;
    link.download = filename;
    link.target = '_blank';
    link.rel = 'noopener noreferrer';
    document.body.appendChild(link);
    link.click();
    document.body.removeChild(link);
    
    // Log download event
    this.logDownloadEvent({
      type: 'normal',
      url,
      filename,
      timestamp: new Date().toISOString()
    });
  }
  
  // Log download events
  logDownloadEvent(event) {
    // In production, send to logging service
    console.log('Download event:', event);
    // Example: sendToLoggingService(event);
  }
  
  // Handle download with full isolation logic
  async handleDownload(url, filename) {
    try {
      const extension = '.' + filename.split('.').pop()?.toLowerCase();
      
      // Check if should isolate based on file type
      if (this.downloadPolicy.alwaysIsolate.includes(extension)) {
        this.downloadToIsolatedEnvironment(url, filename);
        return;
      }
      
      // Check source
      if (this.downloadPolicy.isolateFromUntrusted && !this.isTrustedSource(url)) {
        this.downloadToIsolatedEnvironment(url, filename);
        return;
      }
      
      // Scan if enabled
      if (this.downloadPolicy.scanBeforeDownload) {
        const scanResult = await this.scanFile(url);
        if (scanResult.malicious) {
          this.downloadToIsolatedEnvironment(url, filename);
          // Optionally show warning to user
          alert(`File flagged as potentially malicious: ${scanResult.threatName || 'Unknown threat'}`);
          return;
        }
      }
      
      // Safe to download normally
      this.downloadNormally(url, filename);
    } catch (error) {
      console.error('Error handling download:', error);
      // Fail closed - isolate on error
      this.downloadToIsolatedEnvironment(url, filename);
    }
  }
}

// Usage
const downloadIsolation = new DownloadIsolation();

// Intercept download links
document.addEventListener('click', (e) => {
  const link = e.target.closest('a[download]');
  if (link && link.href) {
    e.preventDefault();
    const filename = link.download || link.href.split('/').pop();
    downloadIsolation.handleDownload(link.href, filename);
  }
});

// Log isolation events
function logIsolationEvent(event) {
  logger.info('Browser isolation event', {
    type: event.type,           // 'isolate', 'allow', 'block'
    url: event.url,
    reason: event.reason,
    user: event.user,
    timestamp: new Date(),
    sessionId: event.sessionId
  });
  
  // Alert on suspicious patterns
  if (event.type === 'isolate' && event.reason.includes('malware')) {
    sendSecurityAlert({
      user: event.user,
      url: event.url,
      severity: 'high'
    });
  }
}

// Track isolation metrics
const isolationMetrics = {
  totalSessions: 0,
  isolatedSessions: 0,
  blockedSessions: 0,
  averageSessionDuration: 0
};

function updateMetrics(event) {
  isolationMetrics.totalSessions++;
  
  if (event.type === 'isolate') {
    isolationMetrics.isolatedSessions++;
  } else if (event.type === 'block') {
    isolationMetrics.blockedSessions++;
  }
  
  // Calculate isolation rate
  const isolationRate = isolationMetrics.isolatedSessions / isolationMetrics.totalSessions;
  
  // Alert if isolation rate is too high (potential attack)
  if (isolationRate > 0.5) {
    sendAlert('High isolation rate detected', { rate: isolationRate });
  }
}

// Integration with SIEM
function sendToSIEM(event) {
  siemClient.send({
    source: 'browser-isolation',
    event: {
      type: event.type,
      url: event.url,
      user: event.user,
      timestamp: event.timestamp,
      riskScore: calculateRiskScore(event.url)
    }
  });
}

// Integration with EDR
function checkEDRThreats(url) {
  return edrClient.checkURL(url).then(result => {
    if (result.threats.length > 0) {
      return {
        action: 'isolate',
        reason: `EDR threat detected: ${result.threats.join(', ')}`
      };
    }
    return { action: 'allow' };
  });
}

// Integration with threat intelligence
async function checkThreatIntel(url) {
  const domain = new URL(url).hostname;
  const intel = await threatIntelClient.lookup(domain);
  
  if (intel.malicious) {
    return {
      action: 'block',
      reason: `Threat intel: ${intel.reason}`
    };
  }
  
  return { action: 'allow' };
}

// Pre-warm isolated browsers
const browserPool = {
  browsers: [],
  maxSize: 10,
  
  async getBrowser() {
    if (this.browsers.length > 0) {
      return this.browsers.pop();
    }
    // Create new browser if pool is empty
    return await createIsolatedBrowser();
  },
  
  async returnBrowser(browser) {
    if (this.browsers.length < this.maxSize) {
      this.browsers.push(browser);
    } else {
      await browser.close();
    }
  }
};

// Use connection pooling
async function openIsolatedURL(url) {
  const browser = await browserPool.getBrowser();
  try {
    const page = await browser.newPage();
    await page.goto(url);
    return page;
  } finally {
    browserPool.returnBrowser(browser);
  }
}

// Optimize pixel streaming
const streamingConfig = {
  quality: 'adaptive',      // Adjust based on network
  frameRate: 30,            // Reduce for slower connections
  compression: 'h264',      // Use efficient codec
  resolution: '1920x1080'   // Standard resolution
};