The structured testing of OSINT and verification tools within the RESONANT framework generated descriptive findings concerning technical behaviour and operational usability. The evaluation was conducted collaboratively by cyberteams A (CT-A) and B (CT-B), consisting of Hellenic Police and Ukrainian Police experts, each working with distinct selections of the mixed-source evaluation corpus under their respective operational conditions. The results illustrate behaviour on the historical evaluation material but should not be treated as statistically representative estimates of general FIMI-detection performance. The observations reflect the specific testing period, available tool versions, dataset composition and evaluator context. OSINT tools evolve rapidly and their functionality, access conditions and performance may change because of software updates, API modifications or platform policies. The results are therefore indicative of methodological applicability rather than fixed performance rankings. The following subsections analyse tool effectiveness and limitations, propose an optimised suite of instruments, and reflect on practical challenges encountered during testing.
5.1 Tools’ effectiveness and limitations
The first category examined was fact-checking tools, which play a fundamental role in the early triage of false or recycled narratives. Across both evaluations, results showed clear disparities in performance. GPT-4o produced the strongest scores within the historical fact-checking tasks, correctly identifying around 90 percent of true and 58 percent of false claims in the CT-A tests, and achieving 94 percent accuracy on true and 95 percent on false claims in the CT-B evaluation, with only minor false-positive rates. The Factual ranked second in the CT-A results, correctly classifying about 52-55 percent of true and 47 percent of false claims, though it showed higher uncertainty levels (up to 45 percent undefined). The CT-B results were broadly similar for true-claim detection, though other fact-checking repositories performed inconsistently on false claims. Traditional databases such as Snopes, Google Fact Check Explorer, PolitiFact, Truth or Fiction, AFP Fact Check, and Fake News Debunker provided limited utility, often returning undefined outputs or failing to match phrasing with their existing entries. These findings indicate that GPT-4o and The Factual were the most informative fact-checking tools on the historical, mixed-source evaluation material, while conventional repositories remain useful primarily for verifying widely circulating or previously indexed claims. They should not be read as evidence that GPT-4o is the most reliable operational fact-checking instrument for novel, emerging, or out-of-distribution FIMI content.
Four caveats qualify these figures. First, because parts of the evaluation corpus derive from or link to publicly documented disinformation cases and third-party collections, GPT-4o may achieve high apparent accuracy by recognising content encountered during training rather than by independently verifying it. The percentages should therefore not be interpreted as evidence of reliable fact-checking on novel or out-of-distribution FIMI content. Second, the exact historical GPT-4o snapshot, prompt, temperature and tool/browsing configuration were not retained, which limits model-level reproducibility. Third, the pronounced divergence between CT-A and CT-B (most notably GPT-4o’s 58 percent versus 95 percent false-claim accuracy) cannot be attributed to the tool alone because the teams used distinct selections and operated under different conditions (Section 3.3). Fourth, no formal inter-rater reliability coefficient was computed and the complete case-level denominator record is unavailable. Accordingly, the accuracy figures should be read as historical agreement with the project-defined labels available at the time, not as externally validated or independently reproducible estimates of general performance. The deposited package improves transparency about the available input pool and metrics but does not make every denominator and output auditable.
The evaluation of website-credibility assessment tools further highlighted the uneven quality of existing resources. While the conceptual value of these tools lies in their ability to provide contextual judgments on the reliability of entire domains, their practical effectiveness was modest. NewsGuard, despite being widely cited in policy discussions, could not be tested due to its subscription-based model, and Schema.org’s ClaimReview lacked the necessary functionality for systematic evaluation. The Know News browser extension demonstrated very limited accuracy, correctly identifying credible or non-credible domains in only about 16 percent of cases. By contrast, MyWOT (Web of Trust), which was integrated after the main testing phase, proved more useful in assessing overall domain reputation. These findings illustrate a broader limitation of credibility-assessment approaches: although they can help highlight recurrent low-credibility sources, their coverage remains narrow and they often require human interpretation to validate results.
When evaluating bot detection tools, the testing process encountered major structural limitations. BotSentinel, once a widely used platform, discontinued its API service and was therefore unavailable for testing. GPTZero, designed primarily for detecting AI-generated text, was tested but could not be effectively applied to identifying automated social-media accounts. The limitation stemmed from the requirement to manually extract posts and comments from platform profiles—an action restricted under Twitter’s terms of service. These challenges highlight a broader issue in bot detection: effective analysis depends on access to authentic behavioral data, yet such access is increasingly limited by platform policies and API restrictions. Consequently, while bot detection remains an essential component of FIMI monitoring, current tools cannot be reliably deployed without sustainable and compliant data-access mechanisms.
The image and video analysis category showed strong and consistent performance, making it one of the most reliable layers of the toolkit. Reverse-image-search tools, including Google Images, TinEye, and Search by Image, achieved 100 percent accuracy, successfully identifying all instances of manipulated or recycled images within the dataset. Tools designed to detect AI-generated content produced more mixed results: ContentAtScale.ai and the Umm-maybe
model hosted on Hugging Face correctly identified about 72 percent of real images and 52–56 percent of AI-generated ones, while Illuminarty.ai performed poorly, detecting only around 20 percent of fake images and generating a high number of false positives. Image-alteration-detection tools, such as FotoForensics and 29a.ch Photo Forensics, also showed uneven but useful performance, both detected 100 percent of genuine images, while achieving 60 percent and 40 percent accuracy, respectively, on altered ones, yet their results required expert interpretation. OCR tools performed very strongly: Google Lens achieved 92 percent accuracy, ChatGPT OCR 88 percent, and OCR.space 68 percent, clearly outperforming older tools such as
NewOCR.com
(28 percent) and
OnlineOCR.net
(16 percent). Taken together, these results indicate that while multimedia forensics is not immune to errors, the current ecosystem of tools for reverse search, AI-image detection, alteration analysis, and text extraction is relatively mature and can be effectively operationalised for investigative use.
The infrastructure-level tools produced more varied results. Geo-IP detection platforms displayed a moderate degree of accuracy. MaxMind GeoIP failed to operate during testing, while IPFingerprints achieved only 36 percent accuracy in identifying the correct country. By contrast,
IPLocation.net
and Thatsthem IP Lookup reached about 70 percent accuracy, indicating that while IP geolocation cannot serve as a standalone attribution method, it provides a useful supporting layer for situating suspicious activity within broader geographic patterns. Phone-number-verification tools showed clearer contrasts:
WhoCalled.com
delivered the strongest results, correctly matching approximately 89 percent of tested numbers in both evaluations and, in several cases, even identifying partial owner information. IPQualityScore’s validator achieved about 65 percent accuracy in the CT-A results but did not return usable data in the CT-B evaluation, as it required manual entry of country codes for each query. Truecaller, despite its popularity, lacked the necessary functionality in its free version and could not be properly tested without login credentials. Overall, the results confirm that
WhoCalled.com
offers the highest reliability for phone-number analysis, while other tools remain constrained by technical or access limitations.
Finally, social-media-analysis tools proved to be the least reliable category. Many of the platforms previously used for extracting or monitoring social-media data, such as CrowdTangle, Ad Observer, and SearchIsBack, are now deprecated, restricted, or entirely non-functional. Tools designed for Twitter, including Advanced Search and Geo-Search
, often returned incomplete or false results, while Facebook-based searches and numerous Reddit utilities such as SubredditStats, Reddit User Analyser, and Apify Reddit Scraper either failed to respond or produced accuracy levels below 40 percent. Several others, including Redective, Keyworddit, and SowSearch, produced errors or unreliable outputs. Overall, the category was marked by discontinued services, false data, and API restrictions imposed by major platforms. This reflects a broader structural issue: as social networks tighten data access, third-party analytical tools rapidly become obsolete. Consequently, while social-media analysis remains essential for FIMI detection, the current landscape is unstable and requires renewed development of sustainable, API-driven, and institutionally supported solutions.
The evaluation of email-verification tools produced mixed but informative results. Among the tools tested, MailboxValidator and Thatsthem Reverse Email Lookup delivered the most consistent performance, correctly identifying around 21–22 percent of valid addresses and providing detailed analytical parameters. EmailHippo produced useful outputs but showed a higher rate of unverifiable results (18 percent) and lower overall accuracy. Emailable and
EmailValidator.com
could not be tested effectively due to account or subscription restrictions. In the CT-B tests, MailboxValidator again demonstrated stable functionality, while Thatsthem provided only partial informational outputs without explicit verification results. Overall, the findings indicate that while several email-verification tools remain limited by access or functionality constraints, MailboxValidator and Thatsthem together offer the most reliable combination for validating contact information within OSINT investigations.
Integrated and cross-domain evaluations
Beyond single-function testing, a series of integrated evaluations was conducted to measure interoperability and cross-domain performance. In the Comprehensive Media Analysis, the CT-A achieved strong, domain-specific results across all stages: 29a.ch Photo Forensics reached 100 percent accuracy in image and video analysis, Originality.ai achieved 89–90 percent accuracy in content verification, and EmailHippo succeeded in all contact-validation tests. CT-B obtained comparable but more qualitative outcomes: 29a.ch Photo Forensics effectively detected image alterations such as cloning but provided limited contextual detail; Truecaller functioned well as a mobile application for identifying spam or malicious phone numbers, and The Factual produced a “Moderately Credible” score of 51 percent for article reliability, performing effectively on most standard-length articles. Taken together, these findings demonstrate that well-configured combinations of content, media, and contact-verification tools can deliver near-complete analytical coverage, though interpretation still requires a degree of manual expertise.
The Disinformation Campaign Analysis revealed mixed levels of effectiveness across the tested tools. For CT-A, The Factual proved highly reliable, achieving 100 percent success in article analysis, while Search by Image reached 43 percent accuracy in image and video verification, and Know News scored 0 percent in social-interaction analysis. These results highlight the strong performance of text-based verification tools but also the need to integrate more robust image-analysis solutions and alternative methods for assessing online interactions. CT-B obtained generally effective outcomes, particularly for article analysis, with Know News performing well in credibility assessment and FotoForensics offering detailed image insights that nevertheless required user expertise to interpret accurately. Overall, the findings confirm that while content-verification tools are mature and reliable, image forensics and social-interaction mapping remain dependent on operator skill and would benefit from more advanced, automated capabilities.
The Cross-Platform Disinformation Analysis produced mixed results. In CT-A’s evaluation, The Factual recorded 0 percent success in article verification, while MediaBiasFactCheck achieved 100 percent accuracy in social-media analysis. CrossRef Search failed to generate relevant matches (0 percent), and MonkeyLearn Sentiment Analysis produced a 40 percent positive versus 60 percent negative sentiment balance. CT-B reported more stable outcomes, with The Factual performing effectively in assessing article reliability. Overall, the findings indicate that while textual and sentiment-analysis tools can yield valuable insights, the ability to establish reliable cross-platform correlations remains limited, highlighting the need for better-integrated analytical frameworks within the current OSINT ecosystem.
Finally, the Multi-Source Disinformation Campaign Analysis assessed the toolkit’s capacity to detect and contextualize disinformation across complex geopolitical narratives. In CT-A’s assessment, The Factual achieved 42 percent success in article analysis, Scribbr AI Detector reached 14 percent in social-media analysis, and
X.com
Explore delivered 100 percent accuracy in cross-reference detection. CT-B did not report available data for this phase. Overall, the results indicate that while content-verification tools can provide partial success in large-scale misinformation environments, automation and cross-modal integration remain limited, underscoring the continued need for human oversight and contextual reasoning in comprehensive disinformation analysis.
OSINT tools: Limitations
Although OSINT tools often seem to be very powerful while conducting digital investigations, due to the automating and fast way of functioning, still they present some significant limitations.
One major limitation is their volatility. In general, digital platforms, social networks, and online repositories constantly change their structures, restrict access, or modify interfaces, depending on various administrative, legal and other reasons. Of course, this also has an impact on an OSINT tool, as these changes may most likely prevent it from functioning. Thus, this constantly unstable situation should be taken into consideration by all interested persons/organizations, who should not rely heavily on any single automated solution.
Next, another limitation is the narrow scope of data coverage. For example, an OSINT tool may be designed to focus on a specific category, such as IP addresses, domain records, usernames, or social media accounts, while leaving many others uncovered, of high importance. This can lead to the conclusion that no single tool can ever provide a complete intelligence picture, and important information can easily be missed if investigations rely solely on tool-generated results.
Another limitation of OSINT tools is the reliability of the generated data. Many tools rely on old, outdated or limited/incomplete sources, which often results in misleading and inaccurate findings. For this reason, it is vital to properly validate and cross-check all resulting information prior to its use or dissemination.
Furthermore, a common risk that someone can fall into is the lack of security measures. This risk emerges from the fact that many OSINT tools interact directly with target platforms (domains), leaving residual evidence in the target log files. This could potentially raise an alert for the administrator, indicating that an investigation is underway. For this reason, proper operational security practices, such as anonymisation, virtual environments, and sock puppets are essential to avoid these risks.
The previous point is reinforced by the fact that there is often an “automation mentality” that gives the impression that OSINT tools are simple, requiring only pressing a button and wait for the results. This creates a false sense of security as, for sure, the tools can assist in the intelligence gathering process, but they cannot replace human creativity, analytical thinking, and reasoning.
Given the rapid evolution of OSINT platforms and access conditions, repeated testing over time would likely produce different operational outcomes.
In summary, OSINT tools are valuable for increasing speed and efficiency, but they have clear limitations. They cannot ensure complete coverage, absolute accuracy, or replace human judgment. Successful OSINT work relies on the investigator’s skills, operational security, and solid methodology, with tools acting as supporting resources rather than definitive solutions.
5.2 Optimised tool suite
On the basis of the comparative evaluation, an optimised suite of tools was proposed for integration into the RESONANT detection environment. At the content-verification level, GPT-4o and The Factual were retained as the most accurate and scalable fact-checking instruments, with traditional repositories maintained in reserve for redundancy and historical coverage. Originality.ai was included as a complementary resource for automated content verification. For website credibility, MyWOT was prioritized as the most consistently usable tool, with Know News included as a secondary option. In the domain of multimedia forensics, Google Images, TinEye, and Search by Image were selected for reverse search; ContentAtScale.ai and the Umm-maybe model (Hugging Face) were retained for AI-image detection; FotoForensics and 29a.ch Photo Forensics were integrated for alteration analysis; and Google Lens and ChatGPT OCR were identified as the strongest performers for text extraction. At the infrastructure level, IPLocation.net and Thatsthem IP Lookup were recommended for IP geolocation, WhoCalled.com for phone verification, and a combination of MailboxValidator and Thatsthem Reverse Email Lookup for email verification.
Although bot detection and social-media analytics remain structurally important, the evaluation concluded that current tools are either deprecated or insufficiently reliable, underscoring the need for further development and integration of sustainable, API-driven solutions. The same applies to cross-platform and multi-source disinformation analysis, where tool interoperability and automation are still limited.
This optimised suite reflects a layered and complementary approach to tool selection. No single tool or category was sufficient to address the full spectrum of adversarial tactics, techniques, and procedures. However, by combining high-performing instruments across content, platform, and infrastructure levels, it is possible to build a detection ecosystem that compensates for individual weaknesses. The proposed suite is therefore not a static configuration, but a dynamic baseline, designed to evolve as tools are updated, discontinued, or replaced.
The recommendation to retain GPT-4o as a content-verification triage instrument must be qualified by the documented tendency of large language models to exhibit systematic biases in evaluative tasks. These include source-framing effects, in which the stated origin of a text (independent of its content) shifts the model’s credibility judgement, as well as broader ideological and political biases in language-model evaluation systems.32,33 Because such biases arise from regularities in training data and alignment processes, they cannot be reliably removed through prompting alone, and they are particularly consequential in geopolitically sensitive FIMI contexts where attribution-adjacent judgements are at stake. GPT-4o is also among the least transparent instruments in the proposed suite. Its inclusion is therefore conditional on operational safeguards: content should, where feasible, be presented to the model without source attribution, and its outputs should be cross-validated against source-agnostic or structured-evidence tools rather than relied upon as standalone verdicts.
Because the suite combines tools that produce structured evidence for analyst interpretation with tools that produce direct verdicts (such as fact-check classifications and credibility scores), its operational use is governed by a minimal decision protocol. First, verdict-producing outputs are treated as investigative leads rather than conclusions and must not, on their own, ground an attributional or evidentiary claim. Second, any verdict intended to inform an investigative action requires confirmation from at least one independent, and preferably source-agnostic, source before use. Third, human analyst review takes precedence over automated output wherever the two diverge, consistent with the principle that tools support but do not replace analytical reasoning (Section 5.1). This protocol distinguishes the proposed suite from a mere aggregation of high-performing tools and treats the automation-mentality caution as a structural safeguard rather than a peripheral note.
Finally, because several of the recommended instruments are commercial, proprietary, subscription-based, or dependent on platform access, and because tool functionality changes rapidly, this suite represents a time-bound baseline valid for the tested period and tool versions rather than a set of rankings generalisable beyond the evaluation window.
5.3 Practical challenges
In addition to technical performance, the evaluation process exposed several practical challenges that must be considered in the operationalisation of OSINT methodologies. The first challenge relates to sustainability: many tools tested were found to be discontinued, inaccessible, or locked behind subscription models, sometimes in the middle of the evaluation itself. This instability undermines the reproducibility of results and highlights the need for a more institutionalized approach to tool provision, potentially through public-private partnerships or open-source development.
A second challenge concerns interoperability. While the testing aligned tool outputs with structured frameworks such as DISARM and AMITT, few tools natively export results in machine-readable or standardized formats. This lack of integration increases the burden on analysts and limits the scalability of detection efforts. Without interoperability, it is difficult to link outputs across categories or feed them into broader intelligence platforms.
Third, the evaluation revealed persistent coverage gaps, particularly regarding multilingual detection and non-Western information environments. Most fact-checking repositories are heavily biased towards English-language content, while many credibility tools assess primarily Western news outlets. This creates blind spots that adversaries can exploit by targeting under-represented linguistic or regional contexts.
Significant ethical and legal constraints arise in the use of OSINT tools, particularly concerning bot detection and the scraping of data from social media platforms. These challenges are especially relevant in operational settings, where strict compliance with data protection regulations (such as the GDPR) and adherence to platform terms of service are required. While controlled, non-operational datasets can help mitigate some of these risks during development and testing, they do not eliminate the legal and ethical complexities involved in real-world applications. As emphasised in the attribution literature, technical observables identified through OSINT tools can support investigations but cannot, on their own, establish responsibility for information influence operations, which ultimately requires contextual, political, and legal assessment.34 Operational usability is another critical factor that can affect the effectiveness of OSINT tools. Even when tools are technically accurate, their practical value may be reduced by unclear user interfaces, non-transparent scoring systems, or steep learning curves. These issues can limit accessibility and hinder adoption by investigators and analysts. Beyond legal compliance, ethical considerations play a vital role in the responsible use of OSINT. Analysts must ensure that their actions are necessary, proportionate and respectful of fundamental rights. This includes avoiding techniques that could be seen as intrusive, manipulative, or misleading. In the absence of universally accepted international standards, OSINT practitioners must rely on sound professional judgment and uphold principles of transparency, accountability and integrity in their work.
A distinction should be drawn between legal-compliance ethics and epistemic ethics. The safeguards described in Section 3.5 (GDPR compliance, proportionality, data minimisation, and the project DPIA) address the lawfulness of data processing. They do not, however, address a separate ethical question raised by the deployment of verdict-producing algorithmic tools in investigative contexts: when an opaque model such as GPT-4o classifies a claim as false and that output informs a law enforcement judgement, the tool functions as an epistemic authority whose reasoning is not, in principle, open to scrutiny or contestation. Non-transparency in verdict-producing tools is therefore not merely a usability concern but an epistemic-ethics concern. Accordingly, the operational protocol set out in Section 5.2 restricts the weight that opaque, verdict-type outputs may carry and requires that they be corroborated and remain subject to human override before informing any investigative action.
Taken together, these challenges highlight the need for a robust, flexible, and ethically grounded framework for OSINT testing and validation. The RESONANT methodology provides an initial foundation by consolidating tool evaluations and aligning them with structured frameworks. However, further efforts will be required to ensure sustainability, interoperability, and accountability in the rapidly evolving ecosystem of FIMI detection tools.