Can ISPs legally monitor and log users' web activity related to child sexual abuse material (CSAM)?

1. The baseline U.S. legal picture: reporting duty, not universal monitoring

Federal law requires interactive service providers to report CSAM once they “know about” it and the REPORT Act broadened those reporting obligations and retention periods for preserved report materials ^{[1] [2]}. But CRS reporting states plainly that federal law currently does not compel providers to proactively monitor their services for CSAM in the first instance — meaning mandatory continuous, blanket scanning is not a settled nationwide legal requirement under existing federal statute ^[4].

2. New and proposed U.S. rules that push providers toward more scanning and retention

Legislation and regulatory changes have moved toward expanding what providers must do after detection and lengthening how long evidence is preserved: the REPORT Act amends 18 U.S.C. §2258A and the Senate passed measures extending preservation from 90 days to one year and expanding categories that must be reported ^{[1] [2]}. Separately, advocacy and some Congressional proposals (e.g., the END Child Exploitation Act) would require ISPs to retain certain metadata for a year — proposals that, if enacted, would increase logging and retention burdens on providers ^[3].

3. Industry tools, voluntary scanning, and partner lists

Technology vendors and many platforms already deploy automated detection (hash‑matching like PhotoDNA, fuzzy hashing) and blocklists maintained by partners such as NCMEC and hotlines; Cloudflare and other vendors offer CSAM scanning tools that rely on hashes and partner lists to flag known material ^{[5] [6]}. Commercial filtering companies market solutions allowing ISPs to block and report CSAM and to produce compliance reporting — but these are industry tools, not federal mandates ^{[7] [8]}.

4. Europe and other jurisdictions: stronger regulatory pressure, but legal safety rails vary

The European Union has proposed a CSAM Regulation that could obligate services to use automated technologies for detection and reporting and to take risk‑based measures; it aims to harmonize obligations across member states while trying to navigate EU limits on “general monitoring obligations” by framing “targeted” and “proportionate” measures ^{[9] [10]}. Critics warn such rules may push providers to scan more broadly or even consider undermining end‑to‑end encryption, and debate continues about scope and safeguards ^{[10] [11]}.

5. Constitutional and privacy constraints: law enforcement searches and court rulings matter

Courts are already testing the limits of reports and downstream law‑enforcement access: a Ninth Circuit decision found a warrantless law‑enforcement review of Gmail attachments flagged as CSAM violated the Fourth Amendment, illustrating constitutional checks on how detected content can be used ^[4]. This judicial scrutiny means courts — not just statutes — shape what monitoring, reporting and subsequent searches are lawful ^[4].

6. Competing viewpoints and implicit agendas

Child‑protection advocates and many legislators argue expanded scanning, retention and mandatory reporting save children and aid prosecutions; industry vendors and some EU lawmakers argue targeted obligations are needed to avoid fragmentation and to enable providers to act ^{[3] [10]}. Privacy advocates and crypto‑experts warn that broad scanning or backdoors to encryption could create surveillance risks and technical impossibilities; commentators explicitly call some EU proposals “science fiction” for expecting reliable AI detection of new CSAM without significant collateral harms ^{[11] [10]}.

7. Practical takeaway for users and ISPs

Available reporting shows ISPs can and do deploy scanning and logging tools and that U.S. law requires reporting when providers become aware of CSAM and is moving toward longer preservation obligations, but federal law generally does not compel blanket proactive monitoring today ^{[1] [2] [4]}. In Europe and elsewhere, proposed regulation may oblige more active detection, but those proposals are contested and include carve‑outs and safeguards intended to limit general monitoring ^{[9] [10]}.

Limitations: this analysis uses only the supplied documents; it does not cover state laws, every court decision, or technical standards beyond the cited materials. If you want, I can map how specific proposed or enacted laws (e.g., REPORT Act text, END Act status, or the current EU Regulation draft) would change ISP obligations in a particular country or state using primary texts.