Defending Bridge Navigation: ECDIS, AIS and GPS Against Spoofing and Jamming

What is actually happening on Gulf bridges right now?#

Two distinct threats are in play, and the distinction drives the defence. Jamming denies the signal; spoofing replaces it with a convincing lie. Spoofing is the more dangerous because the bridge may not notice.

The reason spoofing is so corrosive is that GNSS underpins far more than the chart. GNSS feeds far more than the chart. ECDIS, ARPA, AIS, GMDSS distress positioning and many shipboard clocks all depend on it, so one spoof can corrupt several systems at once. A bridge team that would normally cross-check one instrument against another finds that a single successful spoof does not corrupt one instrument, it corrupts a correlated set of instruments that a bridge team might otherwise use to cross-check one another.

This is no longer episodic. Across 2025 the problem scaled sharply: by Q2, GPS jamming surged, impacting over 13,000 vessels, with geopolitical flashpoints like the Iran conflict driving mass spoofing events and false port calls. In the Gulf specifically, multiple reports indicate significant GNSS and electronic interference across the Arabian Gulf, with potential impacts to positioning, navigation, and communications systems, including AIS and VHF. The effects are exactly what you would expect from spoofing at scale: these effects may produce artificial vessel tracks, unrealistic speed readings, and sudden positional displacement, potentially creating the appearance of vessels transiting across land.

The interference is also geographically concentrated where Gulf operators are most exposed. As of March 2026, JMIC reporting placed the densest disruption near the Strait of Hormuz approaches and adjacent Omani/UAE waters. AIS anomaly mapping also indicates secondary interference patterns extending into the Red Sea, particularly near the Bab el-Mandeb Strait, though the density of disruption appears lower than in the Arabian Gulf.

Two cautions on intensity. First, the picture fluctuates — by early May 2026, UKMTO noted GNSS interference had become sporadic but reduced from the level of activity recorded in March. Second, this is Developing; treat any single day's reporting as a snapshot.

Why can't I just buy my way out with better hardware?#

Hardware resilience matters, but it is one layer, not the answer. The defence stack runs from antenna to bridge team.

On the receiver, the industry direction is clear: implementing multi-frequency and multi-constellation GNSS receivers can improve resilience against GPS interference. Insurers also point operators toward independent backups — exploring the incorporation of alternative positioning systems, such as inertial navigation systems or celestial navigation, can provide backup options during GPS outages.

There is movement on jam-resistant antennas too. In September 2025, the State Department removed jam- and spoof-resistant Controlled Reception Pattern Antennas (CRPAs) from the International Traffic in Arms Regulations (ITAR). That matters for procurement timelines, but it does not retire the human layer. As one maritime cyber team put it bluntly, spoofing exploits trust in a confident display.

How do I harden ECDIS specifically?#

ECDIS sits at the centre of the bridge OT network and is a long-standing entry point. Any breach of ECDIS security could result in ECDIS sensor data being manipulated with unreliable information displayed to the officer of the watch. It could even mean a total loss of the ECDIS and any equipment on its associated network. Two vectors dominate: removable media and the back-of-bridge network used for chart updates.

The IHO ENC/ECDIS cyber security instruction is direct on architecture. The ECDIS should be used for primary navigational use only, and all other data validation and preparation should be carried out on a secure back-of-bridge system/network. Modern automated chart-delivery gateways are designed to remove the USB step entirely, passing updates through a controlled boundary rather than a stick carried onto the bridge.

Practical ECDIS hardening for a Gulf-trading fleet:

The contingency-planning point is now explicit in ECDIS best practice: ECDIS contingency planning addresses power failures, heading and speed input losses, position-fixing system failures, and cyber security incidents including GNSS spoofing and jamming. And paper retains its role — when ECDIS, GNSS, or other digital navigation tools are compromised by a cyber incident, current paper charts allow the bridge team to maintain safe navigation using traditional methods.

What about AIS — should we keep transmitting in the Gulf?#

This is a live operational question, and the honest answer is that it is master- and operator-led, within a SOLAS frame. UKMTO's guidance is consistent: AIS usage remains governed by SOLAS regulations. Operators should review AIS transmission policies within their risk management frameworks while maintaining compliance with regulatory requirements.

Two practical points. First, spoofed AIS positions are a compliance hazard, not just a navigation one. AIS spoofing in the Persian Gulf presents significant challenges for commercial shipping operations, particularly in relation to sanctions compliance. When vessel positions are falsified to appear as if they have called at ports in sanctioned jurisdictions, such as Iran, it can trigger scrutiny from financial institutions, insurers, and regulatory authorities. Keep accurate, independently sourced voyage records so you can rebut a false port-call claim.

Second, any decision on AIS silencing should be coordinated with your flag state and documented in the vessel security plan. Consult your flag administration and counsel before adopting a standing policy.

What does the regulatory framework actually require?#

There is no single anti-spoofing rule. The obligations are distributed, and you should verify current text directly with each authority.

Instrument	Issuing body	What it does	Applies to
MSC.1/Circ.1644 (2021)	IMO	Addresses deliberate GNSS/GPS interference; urges states and operators to act	Guidance; flag states & operators
SOLAS V/19	IMO	Carriage requirement for a GNSS or terrestrial position source usable throughout the voyage	All ships
MSC.428(98)	IMO	Requires cyber risk management within the SMS	In-service vessels since 1 Jan 2021
IACS UR E26 / E27	IACS	Cyber resilience of ships and of onboard systems/equipment	New ships contracted on/after 1 Jul 2024

On the IMO position, the official IMO/ICAO/ITU material confirms the carriage baseline: Regulation V/19.2.1.6 of SOLAS requires that all ships, irrespective of size, shall have a receiver for a global navigation satellite system or a terrestrial radionavigation system, or other means, suitable for use at all times throughout the intended voyage. MSC.1/Circ.1644 itself urged member states to take actions necessary to minimise interference coming from their territory, as required under the ITU Radio Regulations, and to consider issuing warning notices or advisories to mariners. Note the limit: per a flag administration circular, as of the current date, the International Maritime Organization (IMO) has not issued any specific guidelines solely for mitigating GPS spoofing on ships.

On class, the dates matter. IACS has decided to apply only the revised requirements from 1 July 2024. They are not retroactive — E26 and E27 apply to ships contracted on or after 1 July 2024. They do not retroactively apply to existing vessels. For your existing fleet, the obligation runs through MSC.428(98) and the ISM SMS, and E26-aligned practice — asset inventory, OT/IT segregation, vulnerability management — is the sensible benchmark.

What should we do this week?#

Lead with the official advice, because it aligns precisely with good seamanship. MARAD's current Gulf advisory is explicit: significant GNSS interference, spoofing, and jamming continue across these areas. Given the degraded positional integrity environment, mariners should increase reliance on traditional navigation methods including radar ranges, visual bearings, and cross-checking ECDIS inputs with secondary navigation systems.

Concretely, for a Gulf voyage:

• Pre-voyage: brief the bridge team on the interference picture and expected indicators; confirm paper/independent backup is current; verify the position-source feeding ECDIS, AIS and GMDSS.
• On passage: cross-check GNSS against radar ranges and visual bearings continuously where interference is suspected; maintain dead reckoning; keep a VHF Ch16 watch. JMIC's standing advice is to apply disciplined bridge resource management, maintain effective VHF/AIS communications, and cross-check navigation systems where interference is suspected.
• After any event: log the anomaly with time, position and effect, and report to UKMTO. Logging GNSS anomalies, reporting them to the relevant authority, and capturing them in the incident and drill record both improve the regional picture and provide the evidence an IMO cyber audit and a P&I review will expect.

The decisive layer remains the bridge team. That is precisely why independent, non-GNSS references matter so much. Hardware buys you resilience; trained, sceptical watchkeepers are what stop a confident-but-false display from becoming a grounding.

If you operate in the Gulf and want a bridge-OT and GNSS-resilience review mapped to MSC.428(98) and your SMS, book a consultation with Solas Security.